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DEPREX

Recent results of RFCS DEPREX research project – Early detection and prevention ot tuyere damaging conditions for extension of tuyere life time at blast furnaces

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DEPREX project abstract

Up to now the damage of a blast furnace tuyere is an unpredictable incident during usual blast furnace operation, which happens in average between 30 to 120 times a year. Each single tuyere damage effect a stoppage of the whole blast furnace of several hours for repair. Those unplanned stoppages caused by tuyere damage effect:

additional consumption of energy (coke, auxiliary energy, etc.),
additional costs mainly for coke, staff and equipment,
increased risks for severe operational incidents and occupational health
additional emissions (CO₂) and
loss of production.

Although BF operators and R&D institutes have done a lot of effort analysing the tuyere damages and trying to find the reasons for those incidents there are still major gaps what to do or avoid for lowering tuyere damage incidents at BF operation. The main difficulty up to now was the “singular” character of the incidents due to local thermal overload and the massive destruction effect within short time, which has led to an acceptance of those damages as usual in the past. Consequently, no operational tools are available, yet, to solve the problem.

The RFCS DEPREX research project aims to develop an operational online control system for early detection and prevention of tuyere damaging conditions in order to decrease the frequency of unplanned BF stoppages for significant reduction of energy consumption and costs in BF operation.

DEPREX objectives

The damage of a blast furnace tuyere is an unpredictable incident in blast furnace operation. Each single tuyere damage effect a stoppage of the whole blast furnace of about two hours up to eight hours for repair. Although, the hot blast is stopped and no hot metal is produced, coke is consumed and additional coke has to be charged. Energy is spent without any benefit.

The additional energy caused by a BF stoppage due to tuyere damage has been estimated roughly to about 1.600 TJ each year for German BF only. The estimation implied a damage frequency of 45 damages per blast furnace and year. Assuming the same tuyere damage frequency for blast furnaces in EU 28 the useless energy consumption results of more than 6.000 TJ. Doubling the extension of BF tuyere life time gives a benefit of 3000 TJ. Therefore reduction of tuyere damage frequency is an important aim to the sustainable energy use and reduction of costs strengthening the competitiveness of the European iron and steel industry.

The aim of the planned RFCS project is the development of an online BF tuyere damage risk assessment system for early detection and prevention of tuyere damaging conditions in order to decrease the frequency of unplanned BF stoppages. The decreasing number of unplanned blast furnace stoppages due to tuyere damages enables a significant reduction of energy consumption and costs in blast furnace operation. Furthermore, it decreases the risk for the occupational health due to e. g. contact of blast furnace staff with toxic CO containing gas and hot metal during exchange of damaged tuyeres. Therefore, each prevented tuyere damage helps to increase safety of BF staff.

Consequently, the proposed project contributes to the RFCS programme objectives (Council Decision 2008/376/EC).

DEPREX research approach

To reduce the frequency of unplanned stoppages due to tuyere damages an innovative BF tuyere damage protection approach is developed with the project DEPREX. The key idea of this new approach is to detect early indications for BF tuyere damaging conditions before the tuyere damaging process has started and to prevent those conditions with suitable countermeasures in BF operation. Thus, the BF tuyere life time will be extended. The new integrated DEPREX approach is shown schematically in the figure below.

Additional knowledge about BF tuyere damage mechanism and weak spots / areas at tuyeres is generated by advanced analysis of the degradation of BF tuyere material properties over the life time of such components. Up to now metallurgical and thermo chemical investigations have only been carried out at damaged tuyeres. The chronology of material properties of BF tuyeres “from cradle to grave” has never been investigated before and is expected to give important additional information. The additional knowledge about tuyere damaging mechanisms is one key component in the development of the new online BF tuyere damage risk assessment system.

In order to get the necessary thermal data from the BF tuyere area new operational BF measuring tuyeres (MT) with advanced fibre optical temperature measurement device will be developed. The BF measuring tuyeres with fibre optical temperature measurement, generates important information concerning the thermal conditions in the BF hearth for the BF tuyere damage risk assessment system.

The new operational BF tuyere optical monitoring system (OMS) is used for monitoring of the BF tuyere and detection of tuyere damaging conditions. The system generates additional input for the new BF tuyere damage protection system. The new technology can be used as trigger for countermeasures at an early stage. Consequently, the advanced optical monitoring system brings an added value to the early detection of abnormal tuyere operation conditions effecting tuyere damages.

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The data and information generated with the new operational BF tuyere monitoring systems (MT & OMS) together with operational data of the blast furnace are concluded, analysed and processed in the model-based online tuyere damage risk assessment system. The aim is an early detection and prevention of BF tuyere damaging conditions with appropriate counteractions of the BF operators.

The basic idea of this new online BF tuyere damage risk assessment system is, first, to provide new operational BF tuyere monitoring systems improving and combing the prototype measuring tuyeres and the tuyere optical control system established in a previous project. Second, the measuring data will be correlated with operational data of the blast furnace. The results will be exploited for industrial online application in a model based online BF tuyere damage risk assessment system. The new BF tuyere damage protection system is composed of the following modules/ components:

New operational BF measuring tuyeres with advanced fibre optical temperature measurement at the whole tuyere surface extending into the raceway
New operational BF tuyere optical control system with advanced extraction of parameters representing conditions in and in front of the tuyere
Online monitoring system for early recognition of tuyere damage risk combining statistical and model based analysis of operational BF and measuring tuyere data
New process control strategies for different escalation levels of tuyere damage risk

The overall aim of the DEPREX RFCS research project is the early detection and prevention of tuyere damaging conditions for the extension of BF tuyere life time. The decrease of the frequency of unplanned blast furnace stoppages due to tuyere damages effect a significant reduction of energy consumption and costs in blast furnace operation, contributing to the RFCS programme objectives and strengthening the competition of ironmaking in Europe.

VDEH-Betriebsforschungsinsitut GmbH
thyssenkrupp Steel Europe AG
voestalpine Stahl GmbH
ISD Dunaferr Co. Ltd
Furol Co. Ltd
The project leading to this application has received funding from the Research Fund for Coal and Steel under grant agreement No 709424.

The decreasing and fluctuating quality of raw materials and the aim to maximise PCI and decrease coke rates force European blast furnaces to operate closer to operational limits. At same time productivity and efficiency must be raised to survive in global competition. High stack permeability and stable gas distribution become most important.
However, the analysis and control of the stack processes is difficult: Hundreds of measurement values are available nowadays, but they are distributed around the blast furnace and just show indirect “fingerprints” from outside instead of the real internal process information needed (e.g. position of process zones).
New measurement techniques deliver very fast, full 2D information of the top (acoustical gas temperature, burden profile radar), but they are not sufficiently validated and not investigated by research. Instead, the operators are overcharged with even more separate measurement data. No overall process information is available to decide about control actions.
The main idea of StackMonitor is to establish a new hybrid approach of data processing which couples statistical and kinetic process models with several online measurements. This new approach will provide industrial benefit even beyond iron making, since several industrial processes suffer from the mismatch between the vast amount of measurement data and its poor exploitation.

To achieve this aim, StackMonitor establishes the innovative coupled CFD-DEM simulation to support online process monitoring and control, validated with comprehensive high temperature lab trials. Thus, for the first time the interrelations between solids and gas in the upper stack can realistically be described: The percolation, mixing and degradation of material during descent and the corresponding layer permeability.

Online tools for process monitoring, analysis and control are developed and validated in collaboration with three industry partners covering different operational conditions.

Involved Partners in the reseach are

VDEh – Betriebsforschungsinstitut GMBh
Aktiengesellschaft der Dillinger Hüttenwerke
Salzgitter Flachstahl GmbH
Abo Akademi
Oulun Yliopisto

This project has received funding from the Research Fund for Coal and Steel under grant agreement No 709816.

The main technical objective of StackMonitor is to achieve a break-through of Blast Furnace Stack online monitoring for appropriate control against non-ideal stack states. This technical objective is as well a strategical objective of high importance, since it is necessary to make the European Ironmaking industry sustainable in the tough technologic and economic environment.

The plants are forced to handle at same time

raw materials of lower quality,
raw materials with greater quality fluctuations and
lower coke rates in connection with higher PCI rates.

These boundary conditions mutually amplify their negative impacts decreasing permeability and stability of the stack processes which dominate the efficiency and safety of the Blast Furnace process. New tools are needed by research and industry to handle these effects. StackMonitor will provide these tools on a complete new technical level, to enhance productivity and energy efficiency and to decrease CO₂ emissions and costs.

The objectives of StackMonitor will be achieved by a new approach which combines innovative measuring techniques, new simulation methods and laboratory trials. This describes and analyses the physical and chemical processes in the stack on a new level of accuracy and detail. StackMonitor develops and establishes the combined new methods for operational process monitoring, analysis and control in industrial environment.

The following technical objectives are aimed at:

Exploit new 2D/3D top measurements (acoustical gas temperature, radar) to their full potential.
Combine the new and conventional measurements to deliver new high-quality information about the inner stack state.
Establish innovative modelling approaches (e.g. coupled CFD-DEM) for the analysis of industrial plants
Exploit the new modelling approaches to provide extremely important interrelations of solid properties (along the stack) and gas flow on a new level of detail and accuracy
Fuse and analyse all this information in a CFD-based online Stack Monitoring System.
Derive tailor-made control actions based on the new online process analyses
Validate the Monitoring System and the control actions at different sites using operational trials
Disseminate the system to other European Blast Furnaces.

stackMonitor research approach

The development of the online monitoring systems in StackMonitor will be achieved in four major steps which form the work packages in StackMonitor. An overview of the concept is illustrated in the following figure:

2016-09-30-stackmonitor-approach-bat

Enhanced evaluation of new 2D BF top data measurements: The new top measurements will be validated in combination with conventional measurements, operational data and charging data. The influences acting on the top gas temperature measured by a 2D acoustical system will be investigated on different time scales to separate overlapping effects. CFD-DEM-simulations will support the investigations with new fundamental knowledge.
Online determination of permeability of material layers during descent and analysis of stack gas flow: The 2D top data will be evaluated to derive new online information about the charged layers: The structure and descent of each layer will be determined using 3D radar data. A permeability indicator for each charged layer will be determined exploiting short-time changes of the acoustical top gas temperature. This data will be coupled with the change of material properties during descent including the interrelation to the gas flow, both delivered on a complete new level of detail and accuracy by an innovative CFD-DEM model and comprehensive lab trials.
Multi-physics process zone determination by new 2D top data: After removal of charging influences the 2D top gas temperature profile delivers more accurate information about the gas flow through deeper stack zones. This information will be combined with vertical pressure measurements (along the wall) by a new multi-physics, multi-dimensional approach to estimate the cohesive zone profile. Furthermore, CFD flow simulations, online connected to measured data, will be established as powerful new approach to determine the stack process zones.
Synthesis to online stack process monitoring and control tools: The investigations and tools from work steps 1-3 provide fundamentally new information about the stack processes and boundary conditions. Step 4 of StackMonitor will merge this information in online stack monitoring tools, clearly indicating temperature distribution, reaction zones and gas flow. The online tools will be used for recommendation of control actions. A clear industrial validation of all tools will be done at several blast furnaces to assure the transferability for a wide and general use within European steel industry.

stackMonitor – Online Blast Furnace Stack Status Monitoring

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