University of Twente Student Theses

Thinking out of the hot box : a simulation study aimed at the increase of hot charging and average charging temperature at the hot strip mill of Tata Steel IJmuiden by using hot boxes

Wachter, J.C. (2011) Thinking out of the hot box : a simulation study aimed at the increase of hot charging and average charging temperature at the hot strip mill of Tata Steel IJmuiden by using hot boxes.

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Abstract:	Tata Steel IJmuiden produces steel strip products for application in construction works, automobile industry and as packaging material. Steel is produced from iron ore. First, the iron is melted from the ore in a blast furnace and casted into ladles. After several ladle treatments, the pig iron becomes liquid steel. The liquid steel is then casted into the continuous casting machines, which create a solidified string of steel. At a temperature of around 900°C, slabs are cut from the string and brought to the slab yard. Here, slabs are stored and cool down until they are demanded at the hot strip mill. The hot strip mill reheats the slabs to approximately 1,200°C and rolls them into thin, coiled sheets. As part of cost reduction, sustainability, and increasing sales volume, Tata Steel IJmuiden is striving for decreasing throughput times, stocks, and energy consumption. An important initiative contributing to these goals is the so-called ‘hot charging’, in which the temperature of the slabs charged at the furnaces of the hot strip mill is above a certain minimum. In this research we have investigated the contribution of heat preservation boxes (i.e. hot boxes) to the hot charging initiative. We performed a simulation study using historical data of two quarters. The research objective was: “Develop an operational concept for Tata’s future hot boxes in order to increase the percentage of hot charging and average overall charging temperature” We first made an extensive analysis of the current situation, which we thereupon translated into a simulation model. We used the simulation model to (1) imitate a quarter of a year of production and (2) to investigate an ideal situation with hot boxes. The first answers the question what could have been the benefit of hot boxes if they were already in use during the simulated quarter. The latter shows how the performance can be optimized based on different scenarios. To test the logistical performance in the current situation, we also carried out a pilot. Results from the first simulation showed that an increase of XXX% in hot charging and an increase of XXX°C in average charging temperature can be obtained by designating a fixed number of slab types and without changing production planning. The effect is an expected annual energy saving of €XXX and an increase in annual furnace capacity of approximately XXX kTon. Results from the second simulation showed that an increase of XXX% in hot charging and an increase of XXX°C in average charging temperature can be obtained by dynamically designating slabs to the hot box, in a more stable planning environment. The effect is an expected annual energy saving of €XXX and an increase in annual furnace capacity of approximately XXX kTon. In the pilot, by using different destination labels, we designated a fixed number of slab types to a predetermined area at the slab yard. This was our ‘virtual hot box’. The goal of the pilot was to test logistical performance on slab allocation and slab movements at the slab yard. We examined whether the expected hot box slabs received the correct destination label and if they were correctly transported to the virtual hot box. Based on the results, we concluded that under the current way of working abovementioned benefits cannot be gained entirely yet. Our general conclusion is that hot boxes will definitely have a positive effect on increasing hot charging at Tata Steel IJmuiden. The financial benefits are evident, but before they can be realized, a set of operational improvements has to be implemented:  No longer coupling of customer orders to physical stock  Introduction of new slab destination labels to distinguish between hot box- and non-hot box destined slabs  Computerize a prioritization rule in the BètaPlanner (i.e. an IT-system), such that first hot slabs outside the hot box are scheduled, then hot slabs in the hot box, and, finally, cold slabs outside the hot box  Investigate the possibilities to align operational planning of oxygen steel plant and hot strip mill Hence, our recommendation is to implement these improvements prior to start building the hot boxes.
Item Type:	Essay (Master)
Faculty:	BMS: Behavioural, Management and Social Sciences
Subject:	52 mechanical engineering
Programme:	Industrial Engineering and Management MSc (60029)
Link to this item:	https://purl.utwente.nl/essays/61476
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