摘 要
傳統的高爐煉鐵製程雖是現今煉鐵製程的主流，但其煤炭煉焦和鐵礦燒結兩製程會造成環境污染問題，迫使先進國家幾乎停止新煉焦廠與新燒結廠的興建，於是新煉鐵製程是鋼鐵界近來研究之主要課題之一。熔融還原煉鐵法是以煤粒來還原熔融狀態下的鐵礦，來生產熱鐵水的新煉鐵製程，為了要提升熔融還原爐熔煉強度，熔融還原反應速率一定要快，其主要手段為氣體底吹攪拌鐵渣兩相，產生較大反應面積來達成。隨著反應發生，大量氣體在渣相中產生，再加上頂吹氣體，故爐內熔渣有泡沫化現象，若泡沫渣控制不佳，則會產生控制上的困難，所以泡沫渣的控制是非常重要的。

本研究係利用高溫熔渣的導電性質來量測泡沫渣的高度，主要在探討底吹氮氣流量與熔渣鹽基度對泡沫渣強度的影響。由於煉鐵製程中，熔渣中FeO的還原為主要之製程操控變數之一，在本研究中，由量測CO氣體的產氣速率，探討FeO與碳還原反應的反應速率，同時對泡沫渣高度進行量測，期能於實際熔融還原爐內鐵渣反應過程中，對熔渣泡沫化的現象做一詳細的瞭解與敘述，做為新煉鐵製程設計與操作調整之參考。

熔渣鹽基度B2為0.8至1.2，CaO-SiO2-Al2O3-MgO之MgO飽和渣，在陶瓷管內溫度為1500℃下，以內徑為0.1"的MgO陶瓷管，在10到100 Nml/min的實際氮氣流量範圍內底吹入高溫熔渣中，可使高溫熔渣液態化，泡沫最高可達約1.8 cm，而泡沫化指數在0.6至1.1秒間，泡沫渣高度隨氣體流量增大而增高；且存在一臨界氣體流量，在此流量以下，並無泡沫渣產生，隨著熔渣鹽基度B2的增加，臨界氣體流量會隨之減少；氮氣流量低於 50 Nml/min時，熔渣鹽基度B2對泡沫渣高度影響較顯著；在氮氣流量高於 50 Nml/min時，熔渣鹽基度B4的影響較為顯著。利用34.5%CaO-34.5%SiO2-10%Al2O3-21%MgO且含10﹪FeO的MgO飽和熔渣，在陶瓷管內溫度為1500℃下，假設FeO的反應為一次反應，則FeO與碳還原反應速率常數，k，在0.136 1/m2˙s到0.159 1/m2˙s間，所產生的泡沫渣高度為9 cm，可知由FeO與碳還原反應所產生的泡沫渣較底吹氮氣入熔渣中高許多，且泡沫中氣泡直徑分佈亦較廣。

Abstract
Although the conventional blast furnace is still the major iron-making process today, its coexisting coke oven and sintering plant in developed countries are nearly forced to stop establishing due to serious environmental problems. The iron bath smelting process has thus become the major research topics recently. The iron bath smelting furnace is a new process, with FeO dissolved in liquid slag and reduced by coal, to make hot metal directly. In order to reinforce the smelting strength in the iron bath furnace, high smelting-reduction speed is required. Thus bottom-gas stirring of liquid iron and slag phases to achieve a large surface area for FeO reduction has become an important method in the process. Accompanying the reaction CO product gas with the top-blown O2 gas, the liquid slag contains a large amount of gases and it becomes foaming. The control of the foaming phenomenon is one of the important topics in an iron bath smelter.

The aims of this study contain effects of amount of bottom-blown N2 gas and the slag basicity on the slag foam strength. The good electric conductivity of high-temperature slag gives an effective measuring of the foaming height. The study also includes the reaction speed of FeO with carbon by measuring the CO gas production speed and the height of slag foaming as a consequence of the FeO-carbon reaction. Since the FeO-carbon reaction is a major way in controlling the process, It is hoped that this study can be a reference for design and operation of the process.

Important results in this study are as follows. For MgO-saturated CaO-SiO2-Al2O3-MgO slags (B2 from 0.8 to 1.2) smelted in a MgO crucible with I.D. = 0.1" at 1500 oC, the bottom-blown N2 flow rate of 10 to 100 Nml/min gives a maximum slag foaming height of 1.8 cm, with foaming indices ranging from 0.6 to 1.1 sec. The foam height increases with increasing N2 flow rate, with various critical flow rates with different slag basicity. The critical flow rate decreases with increasing B2 of the slag. However, For N2 gas flow rates less than 50 Nml/min, B2 is the dominating factor for the foam height. On the other hand, B4 is the dominating one for flow rates greater than 50 Nml/min.

Experiments show that for a 34.5 CaO-34.5 SiO2-10 Al2O3-21 MgO (wt %) slag with 10 wt % FeO smelted and reacted (with carbon) at 1500 oC, a FeO-C reaction speed constant, k, ranging from 0.136 to 0.159 l/m·s is obtained under the assumption of the reaction being of 1st order. The slag foam height is 9 cm, being higher than that of the N2 gas, and the size distribution of the bubbles in the slag foam is wider than that of the case of bottom-blown N2 gas.

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