Dynamic, data-driven prediction model of molten steel temperature in the second blowing stage of a converter
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摘要: 轉爐鋼水溫度是轉爐終點控制的工藝參數之一,精確的鋼水溫度預測對轉爐終點控制具有重要的指導意義。然而,以往的大多數轉爐終點預測模型屬于靜態模型,只能夠實現對轉爐吹煉終點鋼水溫度的預測,無法實現動態預測,導致模型的作用有限。針對該問題,提出了一種基于數據驅動的轉爐二吹階段鋼水溫度動態預測模型。模型先通過新案例主吹階段的工藝參數,基于案例推理算法找到歷史案例庫中相似案例。再利用相似案例的二吹階段工藝參數并基于長短期記憶網絡(Long short-term memory,LSTM)算法訓練工藝參數與鋼水溫度的變化關系。然后利用訓練好的LSTM模型,計算新案例二吹階段的鋼水溫度變化。最后,利用某鋼廠實際生產數據,研究了不同重用案例個數及神經元個數對模型預測精度的影響,實驗結果表明:模型在重用案例個數為4,神經元個數為10時模型的預測精度最高,此時模型對鋼水溫度的預測誤差在[?5 ℃, 5 ℃]、[?10 ℃,10 ℃]和[?15 ℃,15 ℃]的命中率分別達到40.33%、68.92%和88.33%,模型的性能高于傳統二次方模型和三次方模型。Abstract: Molten steel temperature is a parameter in converter end-point control. Accurate prediction of molten steel temperature is crucial for converter end-point control. However, most of the previous end-point prediction models are static models, which can only predict the molten steel temperature at the end-point of converter blowing and cannot realize dynamic prediction, affording a limited role for these models. To solve this challenge, a data-driven prediction model of molten steel temperature in the second blowing stage in a converter is proposed. First, the model retrieves the similar cases in the historical case base through the process parameters in the main blowing stage of the new case, such as carbon content and temperature of TSC measurement, based on the case-based reasoning (CBR) algorithm. Second, the process parameters in the second blowing stage of the similar cases, such as oxygen flow, lance position, and argon flow, are used to train the relationship between the process parameters and the molten steel temperature based on the long short-term memory (LSTM) algorithm. Third, the trained LSTM model is used to dynamically calculate the molten steel temperature in the second blowing stage of the new case. Finally, the actual production data is divided into five sets for cross-validation, and the model prediction accuracy changes are tested when the number of reuse cases ranges from 1 to 10, and the number of neurons is 5, 10, 15, and 20. The results show that, on the one hand, the prediction accuracy of the model first increases and then decreases with an increasing number of cases, and when the number of reused cases is 4, the prediction accuracy of the model is the highest, indicating that the number of cases is increased when training the model. Improving the prediction accuracy of the model is beneficial; however, the reference value of the case decreases with the similarity of the case, reducing the prediction accuracy of the model. Conversely, when the number of neurons is 10, the prediction accuracy of the model reaches it’s the highest value. The hit rate of the prediction error in the range of [?5 ℃, 5 ℃], [?10 ℃, 10 ℃], and [?15 ℃, 15 ℃] reached 40.33%, 68.92%, and 88.33%, respectively. This paper also establishes the traditional quadratic model and cubic model as well as further proves the effectiveness of the model by comparing the three indicators of these models, namely, the RMSE, MSE, and hit rate.
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表 1 轉爐主吹階段單值型工藝參數統計結果
Table 1. Statistical results of single-value type process parameters in main blowing stage of converter
Influence factors Symbols Maximum Minimum Mean Standard deviation Carbon content of hot metal/% X1 4.5016 3.9496 4.2273 0.0992 Silicon content of hot metal/% X2 0.49606 0.03189 0.2644 0.08119 Manganese content of hot metal/% X3 0.14347 0.07155 0.10811 0.01291 Phosphorus content of hot metal/% X4 0.07953 0.0527 0.065721 0.004375 Temperature of hot metal/℃ X5 1441 1267 1360.3 31.3 Weight of hot metal/t X6 282 263 272.57 3.39 Weight of scrap/t X7 71 40 60.262 6.207 Amount of lime/t X8 20.605 2.063 9.4865 3.6389 Amount of dolomite/t X9 7.991 2.001 4.7244 1.0092 Oxygen amount of main blowing stage/m3 X10 15022 11298 12931 560 TSC[C]/% X11 0.559 0.038 0.24437 0.10683 TSC[T]/℃ X12 1690 1545 1617.3 24.9 TSO[C]/% Y1 0.066 0.018 0.04225 0.00782 TSO[T]/℃ Y2 1705 1620 1663.42 33.71 表 2 轉爐二吹階段工藝參數統計結果
Table 2. Statistical results of process parameters in the second blowing stage of conventer
Influence factors Maximum Minimum Maximum length of time-series/min Minimum length of time-series/min Oxygen flow 66282 m3·h?1 29998 m3·h?1 2 1 Lance position 5553 mm 1598 mm 2 1 Argon flow 2155 m3·h?1 465 m3·h?1 2 1 表 3 相似案例檢索結果
Table 3. Similarity between the new case and similar cases
Heat No. X1/% X2/% X3/% X4/% X5/℃ X6/t X7/t X8/t X9/t X10/ m3 X11/% X12/℃ Similarity 1 4.13317 0.14899 0.09142 0.06122 1377 273 63 5.981 5.276 12884 0.241 1584 2 4.10874 0.09697 0.08969 0.06242 1376 275 63 4.219 4.755 12659 0.207 1577 94.25% 3 4.05288 0.13592 0.0925 0.0605 1394 273 61 5.53 4.545 12878 0.226 1603 93.18% 4 4.04647 0.15276 0.09448 0.05964 1381 272 65 6.081 4.906 13373 0.299 1597 91.95% 5 4.1307 0.14709 0.0927 0.05653 1354 273 65 6.074 4.596 13101 0.303 1586 91.41% 表 4 模型擬合結果
Table 4. Model fitting results
Model Fitting formula R2 Quadratic model $T = - {10^{ - 5} } \cdot {x^2} + 0.03 \cdot x + {\rm{TS}}{{\rm{C}}_{[{\rm{T}}]} }$ 0.994 Cubic model $T = 5 \cdot {10^{ - 9} } \cdot {x^3} - 2 \cdot {10^{ - 5} } \cdot {x^2} + {\rm{TS}}{{\rm{C}}_{[{\rm{T}}]} }$ 0.9987 表 5 各模型預測精度對比
Table 5. Prediction accuracies of each model
Model MAE RMSE Hit rate/% Quadratic model 10.74 13.61 76.50 Cubic model 9.37 11.69 80.67 CBR_LSTM 7.54 9.38 88.33 www.77susu.com -
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