【導(dǎo)讀】性、抗剝落、抗渣性。它的使用延長(zhǎng)了爐襯的使用壽命，是一種廣義的新型節(jié)能。材料，各國(guó)都在大力開(kāi)發(fā)鎂碳磚生產(chǎn)技術(shù)。但是在生產(chǎn)中仍存在易層裂、韌性差。調(diào)整鎂碳磚配合料顆粒級(jí)配、控制混合料濕度與優(yōu)化壓制過(guò)程等措施可。以提高生產(chǎn)質(zhì)量。本文開(kāi)端探討了鎂碳磚的制備。包括原料的選用，意在著重說(shuō)明原材料的質(zhì)。量性能對(duì)鎂碳磚使用效果有較大影響。并介紹了生產(chǎn)工藝流程上主要工藝參。數(shù)的確定及生產(chǎn)過(guò)程中鎂碳磚的層裂問(wèn)題及解決方法。隨之重點(diǎn)介紹了鎂碳磚。在轉(zhuǎn)爐上的應(yīng)用重點(diǎn)闡述了使用環(huán)境對(duì)其使用效果的影響。在論文末章介紹了鎂。碳磚在技術(shù)上的發(fā)展趨勢(shì)。

　　

【正文】 te melting gasifier CorrosionResistant Improvement Effect by theCr2O3 Addition By adding Cr2O3 to other high temperature oxides, the melt generation temperature shouldn39。t been greatly lowered， as shown in Table 1,and it is possible to improve the corrosion resistance of the refractories. 洛陽(yáng)理工學(xué)院畢業(yè)論文 29 Eutectic temperature between Cr2O3 and SiO2 is1720℃ which is slightly lower than melting temperature(1723℃ )of ,the addition of Cr2O3greatly improves the corrosion resistance of the silicarefractories without bringing about the defect. When Cr2O3 is added to Al2O3, they form solid solution, whose melting temperature rises with the increase of Cr2O3 amount and its corrosion resistance is improved. By this characteristic, the Al2O3Cr2O3refractory is used abundantly for gasification melting furnace for the waste treatment. Table 1 Relation between Cr2O3 and high temperature oxides High temperature oxide Compound Eutectic point or melt generation temperature/℃ SiO2 1720 Al2O3 Solid solution 20452265 MgO MgCr2O4 2050(MgOMgCr2O4) 2090(MgCr2O4Cr2O3) CaO CaCr2O4 1930(CaOCaCr2O4) 2100(CaCr2O4Cr2O3) Cr2O3 is added in MgO forming MgCr2O4,whichhas excellent corrosion resistance and 2400℃ of melting point. However, when Cr2O3 contacts with CaO under oxidizing atmosphere such as air, the important problem occurs as described next. 洛陽(yáng)理工學(xué)院畢業(yè)論文 30 3 The Problem of Chrome as A Refractory Component Hexavalent chromium pounds easily form by reactions among the Cr2O3containing refractories andCaO,K2O and/or Na2O,when the refractories contact with waste liquid slag, iron/steel slag, glass ,cement ,etc. ,at high temperature. In CaOCr2O3 system ,the pound CaCr2O4,which is stable under reduction atmosphere ,has a melting point of 2170℃ .The eutectic points between the pound and CaO and Cr2O3 are 1930℃ and 2100℃ ,respectively. Accordingly, there is no problem in coexisting with CaO. However, as oxygen partial pressure like in air is high, hexavalent chromium pound CaCrO4 is stable at low temperature. is an equilibrium phase diagram ofCaOCr2O3CrO3[5].In the case of(CaO/Cr2O3 ≤ 1),trivalent pound CaCr2O4 is stable above 850 ℃or1022 ℃ ,but hexavalent pound CaCrO4 is stable below 850 ℃ or 1022℃ .However, hexavalent chromium pound is stable at any temperature in the case of(CaO/SiO2≥ 1). shows the products of the mixture of CaCO3and Cr2O3 during heating in air 洛陽(yáng)理工學(xué)院畢業(yè)論文 31 atmosphere at5001300℃ .At 6001100℃ ,hexavalent chromium pound CaCrO4 forms ,and trivalent chromium pound CaCr2O4 forms above about 900℃ .That is, the reaction of formula(1)proceeds to the right during heating above about 900℃ . 4CaCrO4+2 Cr2O3 4CaCr2O4+3O2(1) In other words,CaCrO4 reacts with Cr2O3 formingCaCr2O4,though O2(g)is discharged during heating. Compounds in the(CaCO3Cr2O3 equivalent)mixture heated for 2h in air This reverse reaction occurs during cooling. That is to say, trivalent chromium pound CaCr2O4 reacts with oxygen forming hexavalent chromium poundCaCrO4 and Cr2O3. Emission of oxygen brings about mass loss by there action formula(1)during heating, while the mass increase with absorption of oxygen gas during cooling by the reaction to the left side. The experimental result verifies this shows the mass change of the reaction product of the equal mole mixture of CaO and Cr2O3 in repeating heating and cooling in the ℃ ,the mass decreases and increases during heating and cooling ,respectively. 洛陽(yáng)理工學(xué)院畢業(yè)論文 32 Mass change of the mixture CaCr2O4 and CaCrO4) during cooling and heating in air shows the mass change of mixture of CaCr2O4and CaCrO4 in heating and cooling under coexistence heating, the reaction goes to the left side of the formula(1)from about 600℃ ,the mass increases and CaCr2O4 bees further heating ,there action goes to right side of the formula(1)from about1000℃ ,the mass decreases, and CaCrO4 cooling from 1200℃ ,the reaction goes to left side of the formula(1),and CaCr2O4 beesCaCrO4 increasing the mass. Mass change of the mixture (CaCr2O4 and CaCrO4)with Na2O during cooling and heating in air 4 Control of Hexavalent Chromium Compound Formation 洛陽(yáng)理工學(xué)院畢業(yè)論文 33 There are several methods for suppressing the formation of hexavalent chromium pounds, as described below. (1) Temperature control As above mentioned, the trivalent chromium pound is stable above 1100℃ in air atmosphere. Therefore, the generation of the hexavalent chromium pound will be suppressed by holding above this temperature. (2) Atmosphere control during cooling Hexavalent chromium pounds mostly form during cooling from about 1100℃ .Therefore, the formation of such pounds will be suppressed by cooling under reducing atmosphere, for example, in coexistence with carbon. (3) Coexistence with other ponents The formation of hexavalent chromium is suppressed when TiO2 or SiO2 coexists. shows mass change of TiO2containingCaCr2O4 powder during cooling from 1200℃ in air with600℃ /h of cooling rate. The mass change decreases with increasing of TiO2 addition to is,TiO2 inhibits oxidation of CaCr2O4 to CaCrO4 during cooling in air. Mass change of of TiO2containing CaCr2O4 powder during cooling from 1200oC in air 5 Summary 洛陽(yáng)理工學(xué)院畢業(yè)論文 34 One of the important characteristics ofCr2O3containing refractory is excellent when added with other high temperature oxides is also endowed with excellent refractory performance. However, it has the fatal draw back that noxious hexavalent chromium easily forms, when Cr2O3 contacts with CaO,Na2O and/or K2Oponents at high temperature. In this article, the forming conditions of hexavalent chromium pound desare clarified, and the conditions and procedure for