Delft University of Technology
FACULTY MECHANICAL, MARITIME AND
MATERIALS ENGINEERING
Department Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl
This report consists of 68 pages and 16 appendices. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into
Specialization:
Production Engineering and Logistics
Report number: 2012.PEL.7718
Title:
Control of heat and dust development in the steel factory of Tata SteelAuthor:
L.A. Bakker
Title (in Dutch) Beheersing van de warmte en stof ontwikkeling in de staalfabriek van Tata Steel
Assignment: Master thesis
Confidential: yes (January 30, 2018)
Initiator (TU Delft): prof.dr.ir. G. Lodewijks
Initiator (Tata Steel): J. van Dalen
Supervisor: dr.ir. H.P.M. Veeke
Delft University of Technology
FACULTY OF MECHANICAL, MARITIME AND MATERIALS ENGINEERING
Department of Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl
Student: L.A. Bakker Assignment type: Master thesis
Supervisor (TUD): dr.ir. H.P.M. Veeke Creditpoints (EC): 35 Professor (TUD) prof.dr.ir. G. Lodewijks Specialization: PEL
Report number: 2012.PEL.7718 Confidential: Yes
until January 30, 2018
Subject: Control of heat and dust development in the steel factory of Tata Steel
Introduction
From the beginning of the 21 century Tata Steel (former Corus) went through an enormous growth. The Oxygen Steel Factory (OSF2) is part of the manufacturing plant of Tata Steel in IJmuiden. On this site the different stages of the manufacturing process takes place, producing everything from half products to steel or products finished with coating. The oxygen steel factory is a warm and dusty factory, where hot metal arrives in the factory, and after various process steps it leaves the factory as steel slabs (plates). With the increased production rate, this has led to that the emissions and waste flows have increased as well.
Currently the total steel production is about 6,9 million tons of steel a year, but the target is to expand to 7,2 million tons a year in 2012 and even 8,7 million tons in the future. To achieve this, the production rate must increase, and the amount of failures and shutdowns must decrease. The raise of heat and dust distribution inside the factory has worsened the work environment of the employees, and can cause failure within the factory and standstills.
In the past years a lot has changed around the factory, and adjustments have been taken to combat the negative effects. The consequences are reduced but with limited success, due to the absence of information about the source. This all has resulted in consequential damage, for example in the production environment where dust and excessive heat have led to loss of production, material loss and increased cleaning costs.
Problem statement
With all the changes around the factory the cause of the heat and dust is vague. Meanwhile the production failure because of resources has increased, and the cause is not dealt with yet. Because of this it is hard to define focus points where to apply adjustments in the factory. The reliability of the production process has high impact on the achieved production rate. Stabilizing production and increasing the reliability of production process are important steps that have to be made in OSF2.
In the past the reliability of production process was worsened by different changes in the factory. The problem is dust distribution and heat in local areas, which negatively influence the production process. The consequences, cooling, emissions and clean up of the dust, are key performance factors because they can interfere with the process and cause deferments. Because of this aeration, new problems arise with higher pollution and consequential damages of short circuit on crucial places and fall out of employees caused by dust in the eyes (even with protection). With more heat there is an increased burden on the upper cranes and specially on the cooling of the cranes. In order to reduce the disruptive influence of heat and dust on the production process, let’s go back to the cause of the dust to find out which influence the lay-out of the factory has on it, reflecting this knowledge on the current situation, to find adjustments that can be made to
Delft University of Technology
FACULTY OF MECHANICAL, MARITIME AND MATERIALS ENGINEERING
Department of Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl Problem statement
This research mostly focuses on defining the cause of the heat and dust, and gain more information what happens within the factory of OSF2. First the disruptive influence of dust and heat must be researched. This can be done by analyzing what happens within the factory on the field of heat, dust and resources. Comparing the input and output in the areas of ventilation, dust, production and heat will help to identify the source and define how the heat and pollution produced from the process can be reduced. Where did it start and what was the initial plan of the lay-out? What has been changed and which steps were crucial? Which steps can be taken to reduce the influence of heat and dust on the resources and the production process?
When the source of dust and heat is set, implementation can be found to decrease the influence of the dust and heat on the resources. This will result in fewer failures during production, which results in a higher reliability.
Research execution
- Analyze the production process in combination with used resources, according to the Delft Systems Approach
- Analyze the quality and standards of the current production process, the lay-out of the factory and other issues that affect the dust and heat transfer
- Analyze the source of the dust and compare this with the dirt found on different locations through the factory
- Determine the areas exposed with heat and research the ventilation in those areas
- Combine the results found with the experiments with the analysis and find solutions which can increase the reliability
- Study relevant literature
The professor, TU Coach
Preface
In this research the production process and resources around the production process were analyzed to define the de disruptive influence of heat and dust. During this project of seven months I learned about all the important aspects of the total production process of Tata Steel and what happens within the Oxygen Steel Factory. By analyzing information obtained during the research and combining this with information obtained during my own experiments I was able to give Tata Steel recommendations. These recommendations are divided in short and long term implementations, both physically and mentally, which I hope will be implemented soon.
First of all I would like to thank Tata Steel IJmuiden for providing this research assignment for my graduation assignment. Next I would like to thank Hans Veeke, my professor from the TU Delft from the section Production Engineering & Logistics, to his help and guidance through some phases of the project. Further I would like to thank Jaap van Dalen, my mentor at Tata Steel for possibility of doing the assignment, the help, the connections and the guidance through the project. As last I would like to thank all the interviewees for cooperating during this period and for the interesting discussions we have had.
Lene Bakker,
Summary
Tata steel is a big and interesting plant which handles all the production steps from raw materials to strip products. The total supply chain is a balanced chain of products prepared for the client. This research is done in the Oxygen Steel factory (OSF2), the “kitchen” of the steelmaking process. OSF2 is a critical chain in the total plant in IJmuiden. The blast furnaces provide a continuous flow of hot metal, which is a continuous input for OSF2. If the production in OSF2 falls still, this results in immediate production loss for Tata Steel IJmuiden. For the production process the resources around the process play an important part. Since OSF2 was build in 1968 all kinds of problems occurred concerning ventilation problems and dust distribution. A lot has been changed around the factory with new developments around the steelmaking and to provide higher production rates. Research on this has been done in the past but a lot of the recommendations has not been implemented.
The production process is very dependent on the resources used around it. These resources are cranes, materials and employees working with and around the process. Because of the increased production volume the disturbances for the resources because of heat and dust has increased as well. The emissions from some sections of the factory have increased significantly through the years, and the dust in the factory causes a lot of inconvenience. Waste flows are identified per location and combined with different aggregates injected into the process. Heat points within the factory are mostly causes by the production process. On these points heavy cooling is installed. Heat losses also come from the steel pans transported through the factory; but not as heavily as the production process affect the factory.
All these questions and information lead to a problem statement; “Develop an overall concept to reduce the disruptive influence of heat and dust inside the factory” For finding the missing information concerning the problem statement an experimental plan was set up. This experimental plan focuses on getting more information about the heat and dust in the factory and the influence of it on the resources. The experiments were comparing the temperature in different areas of the factory and on different heights levels. Another experiment was to track down the amounts of material that falls down on various locations. The previous waste flows only gave information about the total amount of dust removed from the factory, but with this experiment the deviation could be made between the different halls within the factory. As a third experiment, these dust samples were analyzed to find out more specific about the materials inside the dust. These outcomes are then matched to the location and amount of specific material injected into the production process to get a material flow and determine the percentage of material lost. The last experiment included in the experimental plan is to measure the influence of wind through the factory. The conditions in the factory were compared under different external circumstances as wind directions, and changing the circumstances by opening and closing doors. Before the results from the experiments can be concluded, some additional information is calculated to support the results. This is done for the natural ventilation of the factory and to specify the heat loss from steel pans.
From the results of the experiments different conclusions can be drawn. First of all the heat point are identified. The highest heat load appears to be around the casting process. In the research done in the past this problem was recognized, but the recommendation for how to fix the problem was never implemented. Moreover, the ventilation has been worsened through the years by blocking vents. There is a continuous conflict on the work floor for how to optimize ventilation. If the temperature difference compared to outside gets higher (warmer inside the factory or colder outside), the natural ventilation within the factory will work best. But heat disturbs the resources needed for the production process, so the hall cannot be heated too much An investigation has been done to quantify how much dust is settling down in the various halls and also with materials is collected in the dust. The highest amounts of materials were Fe2O3, CaO and MgO. Relationships are found between the location and method of
injecting materials into the production process and the places the materials were found back. From the wind measurements the influence of wind was mapped. This resulted in advice per season and per hall for what to do with opening the doors on the ground floor.
The combination of a continuous eastern wind through the factory and adding aggregates at the converter results in a dirt distribution through the factory. This results in loss of material and extra cleaning and process costs. Another remarkable conclusion from the research was the enormous excess emission from the LH since 2010. This will costs Tata probably money and is bad for the working conditions inside the factory. The extraction installations on this location should be improved or supported by a third installation.
The situation at OSF2 can be improved by implementing some of the recommendations made to reduce dust and material flows. This will result in improved working environment for the employees, reduced costs and improved standards. Examples could be to return the plating in some areas of the factory, blocking of cross transfers and covering conveyer belts. For example covering the conveyor belt has an payback time of 20 days and save € 144.500, - per year.
For the long term there should be an adapted strategy for ventilation and dust distribution, it should be an integrated approach instead of applying different practices per location within the factory. In this concept it is important to get awareness of ventilation, heat and dust distribution back in the organization, department and the employees within the factory. This will express itself in handling and choices according to certain guidelines which should be secured through the organization.
Summary (in Dutch)
Tata steel is een grote en interessante industrie die alle stappen doorloopt van grondstof tot gecoat staal rollen. De totale supply chain is een evenwichtige keten, gericht op het bereiden van producten voor de klanten. Dit onderzoek wordt gedaan in de Oxy Staalfabriek (OSF2), ook wel de keuken van het staalproces genoemd. Hiermee is OSF2 ook een kritische schakel binnen het gehele productie proces in IJmuiden. De hoogovens leveren een continue stroom van vloeibaar ruw ijzer, wat een continue input voor OSF2 betekent. Als de productie in OSF2 stil valt of vertraagd is, betekent dit dus direct verlies of vertraging binnen Tata. Voor het productieproces spelen middelen die gebruikt worden een belangrijke rol. Deze middelen zijn bijvoorbeeld kranen die de staalpannen intern moeten vervoeren of de mensen die het proces aansturen. Sinds de bouw van OSF2 in 1968 hebben zich allemaal problemen voorgedaan met betrekking tot ventilatie problemen en vuil distributie. Er is veel veranderd in en rondom de fabriek, waarbij alles het doel had om een hogere staalproductie te verkrijgen.
Het productie proces is sterk afhankelijk van de middelen eromheen. Deze middelen zijn kranen, materialen, medewerkers die werken rond het proces Door de toename van de productie zijn de verstoringen van de middelen als gevolg van hitte en vuil ook toegenomen. De emissies van sommige delen van de fabriek zijn door de jaren heen ook sterk toegenomen, wat in combinatie met het vuil in de fabriek voor zeer veel overlast zorgt. Afvalstromen zijn geïdentificeerd en vergeleken met de hoeveelheid toeslagstoffen toegevoegd in het proces. Warmtepunten binnen de fabriek zijn vaak veroorzaakt door het productieproces. Om gevolgen tegen te gaan is op deze punten zware koeling geïnstalleerd.
Deze waarnemingen en feiten hebben geleid tot de volgende probleemstelling; “Ontwikkel een algemeen concept om de verstorende invloed van warmte en stof binnen de fabriek te verminderen”. Om deze vraag te beantwoorden was er meer informatie nodig over de huidige warmte en stof ontwikkeling binnen de fabriek. Voor het vinden van de ontbrekende informatie is een experimenteel plan opgezet. Deze experimenten dienen ertoe om meer informatie te verkrijgen op het gebied van warmte en stof in de fabriek en de invloed ervan op de middelen. Het eerste experiment vergeleek de temperatuurverhogingen tussen de verschillende delen van de fabriek, en bij warme gebieden de invloed van verschillende hoogtes. Het tweede experiment had het doel om de hoeveelheid stof die neerdaalt per locatie te achterhalen. De totale hoeveelheid veegvuil was al vastgesteld, maar daarmee is nog niks gezegd over de verhouding tussen verschillende locaties. In het derde experiment werden deze stofmetingen geanalyseerd om de specifieke samenstelling van het stof te achterhalen. Dit kan dan vergeleken worden met de hoeveel materiaal dat per locatie aan het proces toegevoegd wordt. Het laatste experiment had het doel om de invloed van wind op de fabriek te benaderen. De omstandigheden binnen de fabriek worden beïnvloed door de hoeveelheid deuren die open en dicht staan en de richting en snelheid van de wind, dus door middel van een windmeting werd dit benaderd. Verder was er nog aanvullende informatie nodig om de informatie en resultaten van het onderzoek te kunnen concluderen. Dit is gebeurd op het gebied van ventilatie en de invloed van warmte afgifte van staal pannen. Deze aanvullende informatie bestaat uit een benadering van de luchtstroom aan de hand van een paar berekeningen.
Uit de resultaten van de experimenten kunnen verschillende conclusies getrokken worden. Allereerst zijn de warmte punten gelocaliseerd. De hoogste warmte belasting blijkt afkomstig te zijn van het gietproces. Uit onderzoek uit het verleden is dit probleem al geïdentificeerd maar oplossingen om dit probleem te verhelpen zijn nooit toegepast. Bovendien is de ventilatie door de jaren heen verergerd doordat ventilatie openingen geblokkeerd zijn. Wat betreft de algemene ventilatie is er een continue conflict. Als het temperatuurverschil ten opzichte van buiten hoger wordt, ontstaat er een betere trek en zullen de ongezonde gassen en stoffen sneller de fabriek verlaten. In de zomermaanden betekent een groot temperatuur verschil echter dat het binnen zeer heet moet worden en dat is niet goed voor de machines en mensen werkzaam in de fabriek.
Wat stof betreft zijn de hoeveelheden per hal vastgesteld, hier blijken de LH, CONH en GH1 de grootste overlast te hebben. Qua samenstelling overheersten de materialen Fe2O3, CaO en MgO. Relaties zijn
gevonden tussen de verschillende locaties en de methodes van materiaal toevoegen aan het productie proces. Uit de wind metingen is de invloed van de wind benaderd. Dit in combinatie met de ventilatie berekening heeft geleid tot een advies per seizoen wat te doen met het openen en dichtdoen van deuren bij verschillende hallen.
De combinatie van een continue oostenwind door de fabriek en het toevoegen van toeslagmiddelen bij de converter is één van de oorzaken van stof verspreiding door de fabriek. Dit leidt tot verlies van materiaal en extra schoonmaak- en verwerkingskosten. Een andere opmerkelijk conclusie uit het onderzoek was de enorme toename van vervuiling van de LH sinds 2010. Dit kost Tata veel geld, en is niet goed voor de arbeidsomstandigheden in de fabriek. De installaties op deze locatie moeten verbeterd en ondersteund worden door een derde installatie.
Voor de toekomst van OSF2 en de medewerkers is het aan te raden dat er een aantal dingen aan de huidige situatie toegevoegd worden om de kosten te elimineren en om te voldoen aan de normen. Dit kan gedaan worden door een aantal simpele implementaties toe te passen in de fabriek die leiden tot minder stofverplaatsing. Het terugbrengen van beplating in sommige gebieden in de fabriek, het blokkeren van dwars transportbanen en het overdekken van transportbanden zijn hier voorbeelden van. Het overdekken van de transportbanden zou bijvoorbeeld al binnen 20 dagen terug verdiend zijn en een besparing opleveren van €144.500,- per jaar.
Behalve op korte termijn moet er ook een lange termijn visie komen wat betreft warmte en stof distributie. Een geïntegreerde benadering in een belangrijke factor in deze strategie in plaats van alles per locatie in de fabriek te bekijken. In dit nieuwe concept moet de bewustzijn terugkeren binnen de organisatie, de afdelingen en de medewerkers van de fabriek over ventilatie, warmte en stof distributie. Dit zal zich vervolgens uiten in handelingen en keuzes die gemaakt worden volgens bepaalde richtlijnen. Deze richtlijnen moeten worden geborgd binnen de organisatie.
List of abbreviations
Abbreviation English description Dutch description
CGM Continuous casting machine Continue Giet Machine
CGMH Continuous casting machine hall Continue Giet Machine Hal
CON Convertor Converter
GH1 Casting hall 1 Giet Hal 1
GH2 Casting hall 2 Giet Hal 2
KS Tilting chair Kiep Stoel
LH Loading hall within the factory Laadhal
OSF2 Oxygen steel factory 2 Oxy Staal Fabriek 2
PA Primary extraction installation Primaire Afzuiging
PaCo Steel pan Coordinator Pannen Coordinator
ProCo Production Coordination Productie Coordinator
ROZA Hot Metal put Ruw IJzer put
RY Hot metal Ruw IJzer
RYPO Hot metal desulphurization and deslag installation
Ruwijzer Ontzwaveling- en Afslak Installatie
SA Secondary extraction installation Secundaire Afzuiging
SCH Scrap hall Schrot Hal
SLH Slag hall Slak Hal
TH In between hall Tussen Hal
TOC Theory of constraints Theorie van de beperkende
Contents
Preface ... 4
Summary ... 5
Summary (in Dutch) ... 7
List of abbreviations ... 9
1. Introduction... 12
1.1 Tata Steel ... 12
1.2 Supply chain within Tata Steel... 12
1.3 What is the Oxygen Steel factory? ... 13
1.4 Project description of Tata Steel ... 13
1.5 Report structure ... 14 2. Process description ... 15 2.1 Manufacturing process ... 15 2.2 Resource process... 15 2.3 History ... 16 2.4 Previous research ... 17 3. System approach ... 19 3.1 Blackbox Tata ... 19 3.2 Process TATA... 20 3.3 Process OSF2 ... 20
3.4 Dust development in the process ... 21
3.4.1
Material flow ... 21
3.4.2
Emissions ... 22
3.4.3
Waste flows ... 25
3.5 Heat development within the process ... 26
3.5.1
Heat points from the process ... 26
3.5.2
Cooling ... 27
3.5.3
Natural versus mechanical ventilation... 28
3.5.4
Result of lack of ventilation... 28
3.5.5
Heat coming from steel pans ... 29
3.6 Logistic resource use ... 30
3.7 Process optimization ... 32 4. Problem description ... 34 4.1 Root cause... 34 4.2 Problem issues ... 34 4.3 Problem statement... 35 4.4 Limitations ... 36 5. Experimental plan ... 37 5.1 Situation ... 37 5.2 Method ... 37 6. Results experiments ... 41 6.1 Dust measurements ... 41 6.2 Heat measurements ... 43 6.3 Wind measurements ... 44
7. Dust distribution ... 46
7.1 Cause of problem ... 46
7.2 Consequences OSF2 ... 46
7.2.1
Consequences of dust flows ... 46
7.2.2
Consequences of emissions ... 48
7.3 Approach for improvement ... 49
7.3.1
Improvement of dust flows ... 49
7.3.2
Improvement of decrease of emissions ... 51
8. Heat distribution ... 53
8.1. Cause of problem ... 53
8.1.1
Cause of heat loss ... 53
8.1.2
Lack of ventilation ... 53
8.2. Consequences OSF2 ... 54
8.2.1
Consequences heat loss ... 54
8.2.2
Consequences ventilation ... 54
8.3. Approach for improvement ... 55
8.3.1
Improvement heat loss ... 56
8.3.2
Improvement ventilation ... 57
9. Conclusions ... 61 9.1. Problem statement ... 61 9.2. Boundary conditions ... 62 9.3. Improvements ... 62 9.4. Recommendations ... 64 References ... 66Appendix A: Scientific Research Paper ... 1
Appendix B: List of interviewees ... 6
Appendix C: Factory dimensions ... 7
Appendix D: Steel types ... 8
Appendix E: Steady state model ... 9
Appendix F: Experiment application ... 10
Appendix G: Research done in the past ... 11
Appendix H: Natural ventilation ... 14
Appendix I: Ideal throughput ... 20
Appendix J: Dust concentrations ... 22
Appendix K: Emissions and waste ... 28
Appendix L: Material flow ... 31
Appendix M: Storyboard converter ... 35
Appendix N: Temperature measurements ... 36
Appendix O: Criteria form for implementations ... 43
1.
Introduction
This research on the influence of heat and dust on the production process of the Oxygen Steel Factory is done at Tata Steel in IJmuiden. In this chapter a general introduction is given on Tata Steel, the supply chain on the plant and the Oxygen Steel Factory (OSF2) itself. The essence of the problems detected by Tata is followed in this chapter which leads to a problems description. As last the report structure is described with the structure of the research.
1.1
Tata Steel
Tata Steel, former Corus, is a steel manufacturing plant in IJmuiden. Tata Steel is part of Tata Group, an Indian corporation active in seven major sectors. Tata Group has over 425.000 employees working in 80 countries worldwide, and total revenue in 2011/2012 of 80 billion dollars. Tata Group is called one of world’s fast growing and most reputable corporation [1].
The main focus of Tata Steel IJmuiden is to produce strip products, but there are a lot of factors that can influence the production volume. In 2011 the total steel production was 6,9 million ton, with a production target of 7,4 million ton steel for 2012. To achieve this, the production process has to get more efficient and faster, with less production fallouts. Besides the production growth, Tata Steel IJmuiden tries to deliver the highest possible steel quality. This high segment requires expertise in all the different aspects of the production process. With the financial crisis and the reduced demand of steel, Tata Steel is trying to find new applications of steel products in other markets to produce for.
The focus of Tata Steel IJmuiden can be divided into external and internal goals. The internal goals are the goals set up by the management teams to sell as much steel as possible. For the production process this means that the production rate has to be as high as possible. This cannot happen unlimited though; to be able to produce Tata Steel has to cope with external goals of the environment. Tata steel produces 100% recyclable materials, and reuses 98% of their waste materials. This is why they belong to the most efficient companies dealing with energy efficiency. Because of these external goals Tata has to cooperate with the environment, which sets standards for Tata steel. These can be standards on waste, emissions into the air or noise disturbance for the neighborhood.
1.2
Supply chain within Tata Steel
The production process of Tata Steel is one big chain of links which is balanced for an optimal production. The production process has been optimized in a way that none of the process steps are given a constraint, is a bottleneck for the total process flow. Each step treats the maximum amount of steel which can be handled in that step. In Figure 1 this balanced chain is displayed.
Figure 1: Product optimization Tata IJmuiden
The lead time from a customer places an order until it is being delivered it takes about 5 weeks. It takes a week to connect an order to a roll of steel with certain material properties. Then the pickling takes about six days, cold rolling two days and a hot dip and/or zincing again six days. This together is already three weeks, plus two weeks of transportation time, gives an order five weeks delivery time. Every steel slab that is produced within OSF2 already has a client that will buy it when the final product is ready.
The communication between the planning, logistic processes and production has to be safeguarded continuously, to make sure the efficiency is maximized. When production in one of the links gets into trouble, this can have effect on the rest of the chain. The blast furnaces have a continuous production which is not preferred to set on hold. If there is a disturbance at the OSF2 (downstream of the blast furnaces) because for example the transportation cranes fail, the blast furnaces have to throw away the hot metal. In 2011 the loss at the blast furnaces was 1,05% (63.087 ton hot metal), so reducing this loss would already result in a higher production volume.
1.3
What is the Oxygen Steel factory?
OSF2 is the “kitchen” of the steel making process. The basis is already developed, but it gets adjusted to the ordered steel specification by removing sulfurs, decreasing the Carbon-percentage and specifying the aggregates. OSF2 is a warm and dusty factory, where large amounts of liquid steel are transported from one process to another. There is a lot of heat and dust coming from the steel pans but also from the process itself. This dust swirls around through the factory, causing health problems for employees or unpleasant working conditions. Besides the human problems dust and heat can cause production failure or failure of equipment. In Figure 2 a photo impression is given, where dust is seen underneath the lamps and fumes are visible from the steel pans.
Figure 2: Photo impression of heat and dust in OSF2
1.4
Project description of Tata Steel
The pressure on Tata Steel to produce is increasing. The raw materials are getting more expensive but because of the increasing competition from Asia, the sales are going down. More steel has to be produced in a shorter time, and less interfering or shutdowns can be afforded.
Although this demand is set from Tata Steel, last year a large number of problems occurred within OSF2. All these problems had a different character, but the same cause, the transport of air or the lack of it. The problem has occurred when a sequence of events happened last year. Employees got dust in their eyes, the heat in the halls caused failure of the cranes, monitor flaps on the roof which are taken out of function years ago and short circuit in the electrical room because of the dust there. This caused a lot of
questions; how is the air balance within the factory? Which substance is blown by which airflow? Where does heat apply? Can these air flows and the corresponding dust transport and heat, be improved?
1.5
Report structure
To find out what happens within OSF2 in terms of dust, heat, production, quality of work and resources, first a process description will take place. This is done to obtain more information about the production, the lay-out and detect obstruction of the past. Next the total factory will be analyzed with The Delft System Approach [2]. This will be done by analyzing the process, the logistic use of resources and the dust and heat development from the process. From these analyses a more detailed problem description is given in chapter 4, containing problem issues, research description and limitations. An experimental plan is set up in chapter 5 to fill in the missing information from the analysis, and to define the different situations on different locations in the factory. Next the results of the experiments are given in chapter 6. With the background information from the analysis and the extra information obtained by the experiments next steps for improvements can be made. This is done in chapter 7 (dust) and 8 (heat) which follows the steps cause, consequences and an approach for improvement. This report concludes with conclusions and recommendations for Tata Steel.
2.
Process description
In this chapter the focus will be on the process of OSF2. The resources used within OSF2 will be explored; because of the heat and dust in the factory these can be disturbed. Further the history of OSF2 will be researched, to find out what steps are done in the past, and which obstacles have been encountered in previous research.
2.1
Manufacturing process
The manufacturing process is the main focus for every employee at OSF2. The process consists of ten parts, where the hot metal gets transformed into steel and into steel slabs. The manufacturing process is displayed in Figure 3.
Figure 3: Manufacturing process OSF2
The first component in the figure is the blender (1) which transports the hot metal from the blast furnaces to OSF2. These blenders pour the hot metal into a hot metal pan (2), and thereafter the pan is transported into the factory. Hot metal contains sulfur, which gets extracted in step (3) called the ROZA. This substance holds slag on top, which is scraped of (4). The hot metal pan goes into the converter (5) where it is mixed with scrap and additives to get the required specification for the planned order. Next there are three options, for finishing the steel for the order. First there is the “pan oven” (6), for fine alloying, homogenization of the product, flushing inclusions and heating the steel. The second choice is the coil pan (7) installation, for fine alloying, homogenization of the product and flushing inclusions. The third option is the vacuum treatment (8), for decarbonization, for fine alloying, homogenization of the product, flushing inclusions and heating the steel. At this point the steel satisfies all demands and will be placed in the casting mill (9), where the steel is casted into a plate of about 20 cm thickness, and cut (10) to a length of about 12 m.
2.2
Resource process
The resources used during the production process can be divided into 3 groups; transportation resources, materials used and people involved during the process. These resources are essential for the production process to work. For example without the cranes and the transverse transport systems no steel can be produced at all. It is important to keep in mind the interference between the process and the resources at all times, otherwise the production can fail. For example after step (2) in the process, in the hot metal pit, a crane has to transport the hot metal pan to step (3). The same is the situation for going from steps (4) to (5), getting to (6), (7) or (8) and from there to step (9). These transportation cranes are dependent of different factors; the functioning of the cooling of the cranes or the availability of logistic factors. When the crane cooling is below standard this will result in that the crane will stop as it will not function when the temperature gets too high. This can be because of the electrical machinery within the cranes, but also inside the driver cabin where the crane driver has to control the machine.
Another problem is the dust which affects the resources. If employees cannot do their work because of the dust in their eyes, this leads to problems. Besides, the machinery is affected by the dust too. The cooling systems cannot function when it is full of dust, so extra maintenance has to be planned or it has to be replaced out sooner than expected. Other problems, like a short circuit that once occurred in the motor hall and in electrical rooms on the cranes, can be pretty big performance killers as well, because this affects directly on the converters. The resources are very important to consider when researching the oxygen steel factory and the process. This will be very import to take into account.
(1) (2) (3) (4) (5) (6)
(7)
(8)
(9)
2.3
History
In the past the steel making process was done in a Martin steel factory and an oxygen steel factory (OSF1) [3]. The total capacity of these factories was 3 million tons of steel a year, and by building a new factory (OSF2) the ambition is met to grow to a higher steel production. The factory was built in 1968, designed for the possibility of a production of 5-6 million ton steel a year, which nowadays is increased to about 7 million steel a year. The capacity of the OSF2 is mostly dependent on the capacity of the converters. First there were only two converters, which obtained a capacity of 2,5-3 million ton steel a year, but with the construction of the third converter the capacity was increased to 5-6 million steel a year. With these three converters past year a production rate of 7 million ton steel was obtained. When designing the lay-out of the building it was taken into account that there should be space for a fourth or fifth converter, to further increase the capacity if the plant if desired.
The annual steel production steel has been fluctuating over the years, see Table 1. A growth can be observed, but due to the crisis starting in 2008, this growth has been reduced slightly. Tata Steel IJmuiden has as target for 2012 to produce 7,2 million tons steel, which previously has been achieved only once, in 2007.
Year 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Steel
production
6,12 6,57 6,85 6,92 6,37 7,37 6,85 5,19 6,65 6,94 7,2
Table 1: Steel production through the years in million ton steel a year [4]
The steel making process is warm and dirty, that’s why with the design of the lay-out of OSF2 special attention is set to the ventilation, to reduce the heat load and dust pollution. The goal of this ventilation is to extract the heat, CO-gas and emissions away from the process. The original design contains three halls; a loading hall, a converter hall and a casting hall. The design of the ventilation is done with the combines various aspects to induce initiatives to increase thermal ventilation; adjustable louvers close to the ground, adjustable valves on the roof, separation walls between the walls and prevention of openings in the walls between the louvers and the valves. By dimensioning the openings and ventilation shafts, the released heat and dust that cannot be captured been discharged.
In Figure 4 the thermal ventilation of the original OSF2 is illustrated with the desired wind flows.
The OSF2 started with a loading hall (LH), a converter hall (CONH) and a casting hall (GH). In the CONH most of the dangerous substances from the steelmaking process escape. Consequently, it was decided to keep the CONH separate from the LH and the GH. A few years later it was extended with a scrap (SCH) and slag hall (SLH), on the east side of the building. Later on with the development of continuously casting, in 1991 the last block was casted and the production continued with continuously casting. This resulted in another extension of the factory, this time on the west side of the building, with an in-between hall (TH), a casting hall 2 (GH2) and a slices hall (SH). A section drawing of the new design of OSF2 is shown in Figure 5.
Figure 5: Current design OSF2
2.4
Previous research
From the beginning of the production within OSF2 in 1968, there were lay-out problems concerning ventilation. The complete descriptions can be found in [Appendix G: Research done in the past]. In 1973 the first research was done with wind tunnel tests, to understand more about the ventilation problems. Three main conclusions that can be drawn from this first research [5]:
1: Extension and increasing TH will negatively affect the ventilation in GH1, TH and GH2.
2: It should be avoided that air comes through ducts of spacious openings of the wall to below the casting 3: Expansion of OSF2 between columns 22 and 25 will cause a negative contribution of the wind effect
In Figure 6 the wind tunnel model, a top view of OSF2 and a back view of the transition between GH1 and TH are shown. From citation 1 a conclusion was drawn that the TH shouldn’t be expanded. In citation 3 it was warned for the expansion of the TH and building another building next to OSF2, which happened anyway.
Figure 6: Wind tunnel research (left), top view (middle) and current situation (right)
In 1982 a next research was done by a company named Fläkt to solve on the ventilation problems. Eleven actions were proposed after this research [6]:
1. Mechanically arranging the ventilation flaps in the monitor hood on the roof. 2. Replacement of these flaps.
3. Installing automatically steering in these flaps.
4. Application installation which conditioned air in variable quantities in the continuous casting hall (CGMH) is blown.
5. The mechanically arranging the valves in the roof of the CGMH.
6. Shutting the vents above and below the casting platforms A and B in GH1, if it has not already happened. 7. Installing an adjustable fan air in the casting platforms can blow (max 300,000 m3 / h). Provisions must also be
applied in order to spread the air over the length of the respective platform (which incorporates the movement of the storage under these casting platforms).
8. The application of air locks to common roll and lift doors.
9. Finally, some smaller, local measures can (or should) be taken to ensure the comfort of personnel in certain places to increase.
From the beginning the ventilation flaps on the roof haven’t worked properly, and nowadays they are disrupted and closed 50/50. Neither is the conditioning installation placed in the CGM, nor the fan air to blow on the casting platforms and none of the doors have an air lock.
In 1984 [7] a research is made again because of the complaints about the ventilation around the continuous casting machines (CGM), the proposal is as follows:
1. Instead of ventilation flaps in the casting hall there should be a chimney which does not need controlling
2. The partitions between CGM and GH2 should be closed between the axels 16-21, between the height of 19-34 m. Wall cladding from 34 to the roof should be removed.
3. The air transportation in the north-east on behalf of supply of the ROZA does not influence the climate inside 4. In the cutting hall the outlet openings should be as small as possible
5. The door at the bear pit affects the climate around CGM immediately. When the door is open the climate around CGM 22 gets worse
From this research done in 1984 the conclusion can be drawn that the problems around the CGM are not new. The aeration would be better when certain parts are covered while others are deliberately made open. With the bear pit open a lot of wind flows and dust problems were detected, despite of this research where the conclusion was already drawn that the door should be closed more often.
In 1985 [8] a research was done for dust and vapor disturbance in the main building of the OSF2. The problems occurred on higher levels, were influenced by the process and by the monitor flaps and the ventilation grids. The actions made on basis of this research were:
• Starting at the source; sealing and extraction of the process
• Influencing the air movement
• Covering up the working environments for the employees
The research suggested that there should be further research done at the current ventilation, to quantify the influence of the weather on the work climate and the disturbing sources in the process.
The latest research that could be found was dated from 2001 [9]. Here pressure measurements were done on the roof at the monitor flaps to find out more about the flow direction within the flaps. The conclusion was that there was a minimum of back flow into the factory, but closing the monitor flaps was not recommended because of the delay of outflow of CO.
3.
System approach
In this chapter Tata Steel is going to be analyzed using a system approach. One of the methods is the Delft Systems Approach [2]. First Tata Steel will be analyzed as a Blackbox, then the processes within Tata Steel and finally OSF2 will be analyzed in more detail. From this analysis a further dust analysis is made, and the material flow, waste flows and emissions are set. Combining the dust sources with the material flow gives insights in locations in the factory that should be further studied in this experiment. The same applies to identifying the heat point within the process. Combining the heat points with the resources used in the process the locations where cooling should be applied will be identified. First different ventilation scenario’s will be discussed, to find out the possibilities for the OSF2 of behalf of natural or mechanical ventilation. Then the application of natural ventilation will be approached to see the influence of ventilation. With the help of the theory of constrains, adjustments of the throughput times can be applied to reduce the heat on some locations.
3.1
Blackbox Tata
Tata Steel IJmuiden has as core business producing steel, in the form of steel rolls. The sister company in England has as core business to produce steel rods for the building industry and rails. When considering Tata Steel in IJmuiden as a Blackbox it contains different raw materials as input, the final product in form of steel rolls as output, which has to satisfy certain specifications. This quality is tested on the basis of the performance of the product. The input stream contains iron ore, coal, scrap, oxygen and aggregates. Most of the input material cannot be used directly in the process but will have a pre-treatment before the steelmaking process.
The main end products of Tata Steel are steel rolls, but almost all the other end products of Tata Steel have a second life in a next process or function once it leaves the territory of Tata Steel. The CO gas goes to the Nuon power plant where it is transformed into energy. Blast furnace cement will be used by the cement company Heidelberg Cement. The slag gets filtered, where part of it goes back into the process and part of it will be used in road construction and marine business. Tata Steel IJmuiden has the reputation of delivering high quality steel for the most advanced businesses like automotive and packaging service. The highest quality steel that Tata Steel can produce is used for the packaging of batteries containing chemical materials.
To analyze the total system of Tata, it needs to be structured into processes. Tata Steel is at first approached seen as a Blackbox, then the processes are defined as an aspect system. Finally the aspect systems are put together in a final proper model. In Figure 7 the Blackbox of Tata Steel in IJmuiden is displayed. At the left side the input materials which enter de site are shown, and at the right side the end products which leave the site are shown. In between a lot of processes take place, which have to be done under certain requirements to ensure that the end products which leave the Blackbox have to satisfy the given specifications. Theinternal goals for Tata is reaching the quality steel that is demanded by clients, and offering good working circumstances for employees. The external goals Tata has to compete are mostly the environmental requirements.
3.2
Process TATA
Zooming in on the process of the total steel roll making process there are different processes that can be observed. Distinction can be made between the liquid and the solid parts of the production process. OSF2 is the transition between the liquid side and the solid. First all the pre-processing before the steel making process has to be done. Iron ore and coals are transported by ships and the material is stored in the harbor of Tata Steel. The iron ore is separated in fine powder and very fine powder to be transformed into pellets or sinters. The coals are transformed into cokes, where the three raw materials are mixed in the blast furnaces and hot metal gets tapped from underneath. Within the melting blast furnace cement and CO gas are formed. The hot metal is transported to the oxygen steel factory where by lowering the C-content it results in steel, this process is called the oxidation process. When the steel has got the perfect composition, it is casted into steel slabs and numbered with the right order number. Because of the distance between OSF2 and the hot strip mill the slabs cool down during transportation and get heated before they get rolled into steel rolls. When a client wants the roll thinner or coated, the rolls will continue into the cold rolling or the coating factory.
Tata Steel IJmuiden has a newly developed direct sheet plant (DSP), which can cast and roll the steel into a steel roll without the cooling and heating up again part. This saves energy and time, because the heat coming from the steel plate is directly used in the rolling process. This development design by Tata Steel is a promising one for the future, because the steel can get thinner without losing quality. Between OSF2 and the hot rolling the throughput is continuously minimized for energy savings as well.
The total supply chain of the processes of Tata Steel is displayed in Figure 8. On the left side the input of raw materials go into the system and on the right the output of end products are shown. From above at the different stages in the processes materials enter the system and the waste materials leave the system on underneath. With a dotted line the processes within the OSF2 are displayed.
Figure 8: Detailed process Tata Steel IJmuiden
3.3
Process OSF2
The next step is to zoom in on the process of OSF2, to find out which more detailed processes happen within the factory. The oxygen steel factory is the “kitchen” in the steelmaking process. The basis is already there and through this process it gets turned into steel. The production of hot metal is a continuous process, which is transported to OSF2. Scrap is recycled steel sorted on weight and steel properties. Other input materials are aggregates like lime or aluminum, which determine the specific steel properties and oxygen, for binding the carbon particles in the iron. The output of the steel making process is CO gas (which result from the oxygen-carbon binding process), slag (a thick layer on top of the steel pan consisting of aggregates and pollution in the steel) and steel slabs.
Steel contains different elements, where carbon (C) has the biggest influence on the material properties during production and use. Other elements in steel are Manganese (Mn), Silicon (Si), Phosphor (P), Sulfer (S) and rest elements as Copper (Cu), Chrome (Cr), Nickel (Ni), Molybdenum (Mo) and Tin (Sn).
The steel slabs have to satisfy specific requirements as demanded by the customer. Mainly these requirements have to do with the carbon content of the steel. This carbon content even fluctuates within the steel pan, which is displayed in Figure 43 in [Appendix D: Steel types] [10]. After every process that influence and handles the steel, the quality and the performance of the product is tested, and linked back into the process before the steel continuous to the next step. The steel quality is different in all phases of the steel pan. Only the middle of the steel pan is the best quality (low carbon steel); the rest of the slabs will be used for other clients with corresponding requirements. There are different types of steel that can be made in OSF2.
The oxygen steel making process is a process existing of different components in different machine halls. The architectural division of the factory determines the communication and handlings around the process. In total there are six working units in OSF2. Within these six working units eight processes are performed. In Figure 9 the total process of OSF2 is shown, with the different additions added to the process. The elements added and extracted are based on 1 ton steel [11]. This process model of OSF2 is one part of the total system. This is the production aspect of the system; where other aspects can be expressed in a similar way, for example the order process, the resources that are used or the financial model. In this case the reliability of production is the most important aspect because this is the highest performance indicator and the dust and heat development will arise within the production process.
Figure 9: Detailed process of OSF2
In the figure above values are added with the different elements which are injected into the production process and the elements which are extracted from the process. Some elements are specified but others are still unknown. For example at the vacuum treatment, circulating and electrocute aggregates are injected, but these are not specified. The composition of this could be scrap, lime, ore or dolomite. Summing these elements gives a gab of 102 kg per ton steel, which is about 10%. This difference in material flow needs more research. This will be done in [3.4 Dust development in the process].
3.4
Dust development in the process
3.4.1 Material flow
In Figure 9 the different elements which enter the process are already given, but most of them are not specified yet. In Table 2 the general input and output of OSF2 is given needed for 1000 kg steel. This is an indication which is not complete yet.
Input [kg] Output [kg]
875 Hot metal 1000 Steel
223 Scrap 90 Slag 3,2 FeMn 3,3 SiMn 27 Lime 6,8 Ore 13 Dolomite
These material flows are now transformed into a sankey-diagram, Figure 10, based on 1000 kg steel. The blue flow is the hot metal, which is converted in the yellow flow, to steel. The green flow is the scrap which is added in the converter. There are three points where slag is removed; from the ROZA, from Converter and after casting. The arrows above are the locations where dust leaves the system, but these are negligible compared with the material flow of steel.
Figure 10: Sankey diagram material flow OSF2 based on 1000 kg steel
Summing Table 2 leaves 60,4 kg of “lost materials” for every 1000 kg steel, which is 6% of the total material flow. A more detail figure can be made of Figure 9 for specifying the aggregates; this is done in Figure 11. The different elements entering or leaving the system are shown with colored dots, with the legend on the left side.
Figure 11: Theoretic material flow OSF2 [12]
This amount of missing materials mentioned earlier can be sorted into two categories; emissions and waste. Emission can be defined as “Pollution (including noise, heat, and radiation) discharged into the atmosphere by residential, commercial, and industrial facilities”. Waste is defined as “eliminated or discarded as no longer useful or required after the completion of a process”.
3.4.2 Emissions
To understand the relation between the process, emissions and the dust development within the factory, it has to be distinguished between the different sources of the different dust developments. Next the material flow has to be determined to compare the input and the output of the material flow, to identify the “missing” part. Thereafter the emissions will be looked in more detail, to find out where the various elements from the production process have ended.
• Dust from the conveyer belt through the factory: Within the converter the aggregates have to be transported through the factory to end up at the right destination. These aggregates come into the factory on an open conveyer belt which ends on top of the conveyers. Most of the aggregates are dusty materials like chalk or dolomite.
• Dust development from the process: As shown in Figure 2 there comes fume from the steel pans when they are in transport or when standing in a hall. In these fumes and emissions there is a large content of dust, which will end up in the factory or disappear in the outside air. The main focus of this research is to quantify the dust development in OSF2 from this process.
• Dust from unpaved surface: This is not a source of dust, but does stimulate the dust distribution through the factory. Within the factory 50% of the surface is unpaved, and with a design based on thermal ventilation, it is understandable that there will be a dusty environment. These unpaved sections are mostly a combination of circumstances what happened in the past and was never changed unless it was a hinder for the process. The areas that have been paved are done so with unused steel slabs to be able to park the steel pans.
In [2.3 History] the growth in production rate was mentioned, but this increased production also has influence on the environment of Tata Steel. In Figure 12 the production rate is shown, compared with the total emissions of Ijmuiden, the total emissions of OSF2 and the emissions coming from the roof of LH.
Figure 12: Graph past six years of production rate [13]
The gap because of the economical crisis between 2008 and 2009 is visible, but it is remarkable that the total emissions stay almost constant. Zooming in on the emissions at Tata Figure 13 gives more insight on the emission relations within Tata Steel.
Figure 13: Comparison past four years of total emissions IJmuiden, emissions OSF2 and LH [13]
Following the emissions of OSF2 (green line) there can be concluded that the emissions within OSF2 is increased a lot in the period 2008-2010, but started to decrease after that. For the emissions from the LH (purple line), only increase is found. Between 2009 and 2010 almost a doubling of emission has taken place. What happened between these years is interesting to find out for tackling the problem. This can be a change in handling, chance of materials or change in installation. The percentage of emissions from the LH compared with the total factory of OSF2 is increased from 49% in 2008 to 83% in 2011. A more specific analysis of emissions in the past for years in OSF2 can be found in [Appendix J: Dust concentrations]. 0 2.000.000 4.000.000 6.000.000 8.000.000 2006 2007 2008 2009 2010 2011 A m o u n t S te e l [ to n ] Year production [ton] 0 500.000 1.000.000 1.500.000 2.000.000 2008 2009 2010 2011 A m o u n t e m is si o n s [t o n ] Year total emission [kg] emission OSF2 [kg]
Figure 14: Comparison past four years of total emissions OSF2 and LH [13]
Tata Steel is under strict regulations for that there will not be too many emissions to the environment. The whole site is ISO 14001 classified, which means: “Environment in which an organization operates, including air, water, soil, natural resources, flora, fauna, humans and their interrelationships”[14]. Each year Tata pays about 100 million euro at environmental costs. This money is spent on permits at local governments. This amount is spread over all the steps within the process are specified for emissions, dust, noise and waste.
Focusing on emissions all the airflow exits are checked and the monitoring on it is strict. OSF2 is responsible for about 7% [15] of the dust emissions of the total site of Tata Steel. The municipalities in the neighborhood of Tata Steel are pressing higher demands on the emissions levels through the years. It is a challenge to answer to these demands to the environment. In Table 3 the amount of emissions of OSF2 is compared with the total emissions of Tata Steel IJmuiden.
Emission Amount Tata Steel [ton] Amount OSF2 [ton]
Particulate matter (<10 μm) 1136 102
Sulfur Dioxide (SO2) 3.019 0,3
Mercury (Hg) 0,3 0 (0,4 kg) Arsenic (As) 0,3 0 (5,4 kg) Cadmium (Cd) 0,9 0 (32 kg) Nickel (Ni) 0,7 0 (10 kg) Chrome (Cr) 0,6 0 (19 kg) Lead (Pb) 29 0,9 Zinc (Zn) 4 2 Chloride (CL2) 0,2 0,1
Table 3: Amount of emissions Tata Steel territory and OSF2 2010 [14]
Table 3 compares OSF2 with the rest of the site, but within OSF2 the dust locations have to be defined. The desired output is of course the steel slabs, but there are other favorable and unfavorable outputs as well. To quantify the amount of dust (rough and fine particles) a material flow has to be made to compare the input with the output. It is hard to determine all the parts that arise from the process because some of the materials will return in the process later.
All over the factory there is dust development of which a percentage will leave through the extraction mechanisms or through roof emissions. The amounts are displayed in kg a year at each extraction chimney (numbers 1-5) and roof emission (numbers A-J). For the research the solids are the most relevant to be measured, because these cause the troubles within the factory. Each extraction chimney or roof outlet will have specific amount of dust that will pass the exit. In the further research the gases like CO/CO2/HF and NOx will be neglected, Table 4. Category [A-J] is dust emitted to the air, where
category [1-5] leaves the factory through extraction mechanism.
Location amount
1 De dusting hot metal pit 6.238 Kg/year
Total: 67.243 kg/year
2 Primary extraction 9.952 Kg/year
3 Secondary extraction 9.744 Kg/year
4 Chimney VPBI 29.919 Kg/year
5 Extraction CGM 11.390 Kg/year 0 50.000 100.000 150.000 200.000 2008 2009 2010 2011 A m o u n t e m is si o n s [t o n ] Year emission OSF2 [kg] Emission LH [kg]
A Emissions hot metal pit 2796 Kg/year
Total: 130.467 kg/year B Loss at primary extraction 9.952 Kg/year
C Emissions roof Loading hall 108.548 Kg/year E Emissions roof Casting hall 1 3.000 Kg/year
F Emissions VPBI 166 Kg/year
G Emissions roof Casting hall 2 3.000 Kg/year
I Emissions CGM 3.000 Kg/year
J Emissions transfer cases 5 Kg/year
Table 4: Amount of emissions through different locations of OSF2 2011 [16] (excluded CO/CO2/HF/NOx) Summing these amounts is done in Table 5. The extractions from with the gasses are compared with the extractions exclusive gasses (Table 4), and the emissions. The total of the extraction (exclusive gasses) and the emissions is 197.710 kg a year. Calculating this back to 1 ton steel this is only 2,973E-5 kg (0,003%). This is only a small amount compared to the total flow.
Extraction excluded gasses 67.243 Kg/year
Emissions 130.467 Kg/year
Total lost material 197.710 Kg/year
Table 5: Emissions versus extraction amount
To understand the relation between the injection of the process and the emissions, the flow within the factory has to be defined. To find out how the different materials are being transported from one place to another, there has to be determined where the different materials come from. In Figure 15 the relation is set between the process and the outlets/extraction points. The different materials are characterized with colored dots, and displayed in the process (input) and at the point they are measured outside the factory (output). The factory is now a “blackbox”, because the materials are not traceable within the process yet; this should be further researched with waste flows and experiments.
Figure 15: Material flow combined with the emissions
3.4.3 Waste flows
Knowing the input, output and emissions, the rest of the “missing” material should be waste flows which are removed from the factory. This can be dust removed from the floors or crane ways, but also material transported from one place to another which losses part of it. In [Appendix K: Emissions and waste] the amount of dirt per month removed is shown. The total amount is summarized in Table 6 with costs per ton and the total costs in €.
Dust location Amount [kg] Costs [€ per ton] Total [€ per year]
Ferreous dust craneways 53.040 20,40 1082
Ferreous dust crane girders 157.200 20,40 3207
Lime dust under conveyer belts 210.160 61,20 12862
Wiped dirt floors 234.100 20,40 4776
Roof dust 48.600 39,75 1932
Table 6: Processing costs waste [17]
Besides processing costs there are also cleaning costs. These costs are not specified p ton, but the total amount of costs p year was available. Compared with the processing costs per ton the cleaning costs will mostly depend on the man hours of cleaning. These costs are given in Table 7.
Dust location Total [€ per year]
Ferreous dust craneways
29.174
Wiped dirt floors
266.575
Lime dust under conveyer belts
107.978
Roof dust
4.357
Tabel 7: Cleaning costs waste [18]
When making a short summery the materials of Table 6 and 8 get distinguish into three categories; in, rest and out. Calculated back to per 1 ton steel, the amount of emissions is 2,97E-5 kg and the amount of waste is 1,10E-4 kg. This table is given in Table 43 in [Appendix K: Emissions and waste]. This confirms the Sankey in Figure 10 that the dust does not play a significant role for the production process; it but is still important to research because of the consequences for the environment and the internal working environment. The gap between in the input and output still exists. Even though the emissions and extraction with the gasses would be included, the total “rest” group would still be 1,9E-3 kg per ton steel.
In the analysis the material flow, emissions and waste flows are known, but the factory is still a blackbox. No information is available about the amount of dust that falls down in the factory, and the difference per hall. Neither is there information about the composition of the dust, except that a large amount is probably iron oxide. For information has to be gained about these elements.
3.5
Heat development within the process
3.5.1 Heat points from the process
Heat development is a returning theme in the steel making process. The different stages of steelmaking generate heat and the internal transportation of the steel pans through the factory, cause high temperature in some areas in the factory. A cause of these high temperatures is a lack of ventilation in some areas or the lay-out of the factory. Dependent on the location and the activities in the hall there is a temperature difference in the halls. In the process there are three points where heat is added to the process and four points where heat losses take place (Figure 16). Adding heat is mostly performed by provoking the process by adding aggregates, in the different sections of the factory.
Figure 16: Heat loss points within the process
Heat supply
It can be fatal for the production process if there is too much heat in high areas. When the temperature on the cranes exceeds 55 degrees, the cranes go out of order and the total process will stand still. When there is a certain place in the factory where the heat cannot escape, this can cause troubles in the summer. The cranes where no failure is permitted are in the LH, GH2 and the one which exchanges the Transfer cases at the CGM.
It is known since a couple of years that around summer time the temperature on high levels has to be watched, but an integral approach is missing. Cooling has been applied on the production cranes, so solve part of the problem, but an integral overview of the temperature difference between different areas is missing. In the past the consequences are mostly dealt with instead of the sources. Instead of applying high standards on all cranes it is better to find out the circumstances in each area and apply demands based on these. To be able to do that integral temperature measurements are needed and difference in height has to be researched.
3.5.2 Cooling
As said before, when there is talking about heat, cooling plays a significant role in the total process. Cooling down the equipment is an important key performer of the process to make the material more reliable. Key performer means that if that part fails, it will directly reflect on the process and shutdowns can occur. This can result in missing a production load (335 ton), which costs €225.000 (per load). The cooling takes place mostly on the cranes, and within the control cabins. In Figure 17 the cooling points are shown where there is special focus.
Figure 17: Cooling point within OSF2
These coolers are big relatively expensive equipment where a lot of attention is given to, because with an increasing production level and shorter throughput times no production loss can be permitted. The external heat load that is on these cranes have two causes; first of all are they active in halls where most heat loss from the steel pans occurs, with additional heat release (heat by convection). Secondly the cranes transport the pans of steel or hot metal from one location to another, with a distance between the hot pan and the crane of 3 meters (radiant heat).
