共查询到19条相似文献,搜索用时 171 毫秒
1.
选取有机废液中常见的钠盐(氯化钠、碳酸钠、硫酸钠、甲酸钠、乙酸钠、草酸钠),通过热重分析仪,在25~1400℃考察其高温挥发特性。基于Gibbs自由能最小原理,对Na Cl、Na2CO3及Na2SO4的挥发特性进行热力学计算。结果表明,在N2气氛中,Na Cl在达到熔点后以气态Na Cl及气态Na2Cl2的形式释放,Na2SO4升温至885℃分解生成Na2O,同时Na2O分解,并以Na单质形式释放。而有机羧酸钠盐在600℃之前均热解为Na2CO3,继续升高温度则分解为Na2O,同样最后以气态Na单质的形式释放。在空气气氛中,由于O2的存在,抑制了Na2O的分解反应,致使Na2CO3分解速率小于N<... 相似文献
2.
准东煤燃烧过程中Na2SO4的形成会造成锅炉受热面沾污、尾部SCR催化剂失活等问题。烟气中Na2SO4形成及转化规律的研究对于预测和控制燃煤烟气中Na2SO4的形成有重要意义。发展了烟气中Na/Cl/S/O/H化学动力学模型,研究了烟气中Na2SO4的生成过程及转化机理,考察了含氧量、温度、SO2浓度、H2O浓度等因素对Na2SO4生成的影响。动力学计算结果表明,模型预测结果与实验数据吻合较好,验证了模型的准确性。烟气中的高氧气含量有利于Na2SO4的生成。高温加快化学反应的同时,抑制了Na2SO4的生成。SO2和H2O的影响效果受温度影响较大。反应路径分析表明,Na2SO4的生成路径有两个:一是依赖于SO2直接氧化(NaCl→NaSO3Cl→NaHSO4→Na2SO4),二是依赖于SO2间接氧化(NaCl→NaO2→NaSO4→NaHSO4→Na2SO4)。敏感性分析结果表明,Na2SO4的生成主要对系统中生成或消耗自由基的反应更为敏感。 相似文献
3.
研究了取自某炼化公司废液焚烧余热锅炉不同部位换热面的多个沉积样品,分析了不同部位换热面沉积生长物的组分与沉积机理。利用X射线衍射分析仪(XRD)、扫描式电子显微镜(SEM)以及能量弥散X射线探测器(EDX)分别来鉴定样品的结晶物成分、形貌以及元素组成,各个样品的灰熔融特征温度在智能灰熔点测试仪上测定。结果表明,余热锅炉高温入口段主要沉积物为Na2SO4、NiO、Fe2.3Si0.7O4等,炉膛中低温区域主要出现Na2Ni(SO4)2?4H2O、Na3Fe(SO4)3及 Na6Fe(SO4)4等物质沉积。这主要是由于硫酸钠与受热面管壁氧化保护层(Fe2O3)发生高温腐蚀引起的。 相似文献
4.
蛋白土具有良好的应用前景,但是其自然白度较低制约了其开发应用。蛋白土硫酸铵煅烧法可去除其中的显色金属氧化物,提高蛋白土的白度,同时提取其中Al2O3。本文采用热重-差示扫描量热(TG-DSC)、同步热分析与红外质谱(TG-FTIR-MS)联用系统,结合X射线衍射对煅烧过程的固相及气相产物进行了表征分析,明析了其化学过程。结果表明,蛋白土中的Al2O3和Fe2O3在200~350℃时反应生成(NH4)3(Al,Fe)(SO4)3,同时逸出NH3和H2O;350~450℃时,进一步反应转化为NH4(Al,Fe)(SO4)2,同时逸出NH3、H2O、SO2和O2;450~550℃时,NH4(Al,Fe)(SO4)2分解生成(Al,Fe)2(SO4)3,同时逸出NH3、H2O、SO2和O2;550~750℃时(Al,Fe)2(SO4)3分解生成Al2O3和Fe2O3,同时逸出SO2和O2。采用Kissinger微分法与Ozawa积分法分别计算出4个阶段表观活化能后取二者平均值,分别为101.74kJ/mol、104.52kJ/mol、201.40kJ/mol、232.51kJ/mol,并获得对应4个热化学反应阶段的频率因子、反应级数和动力学方程。 相似文献
5.
采用(NH4)2S溶液吸收净化高浓度SO2烟气,得到(NH4)2S2O3和NH4HSO3的混合溶液并转移至高压反应釜中,控制反应条件,两种物质发生自氧化还原反应,生成硫磺和(NH4)2SO4.实验考察了吸收SO2过程和自氧化还原过程的影响条件,结果表明:在pH=3~7,SO2气体流速300 ml·min-1,(NH4)2S浓度为0.2~1.2 mol·L-1,常温条件下,烟气中二氧化硫的吸收率达到99.8%以上,且无H2S生成;在pH=2.5~3.0,温度为130℃条件下,反应进行1 h,硫磺收率达到95%以上,溶液经过蒸发结晶得到(NH4)2SO4.用X射线衍射(XRD)和X射线荧光光谱(XRF)对硫磺和硫酸铵进行表征分析,结果表明:硫磺的纯度为99.14%,硫酸铵中氮元素含量为23.6%. 相似文献
6.
针对高硫、高钠的高放废液玻璃固化过程中Na2SO4极易分解和分相的问题,本文提出在模拟高放废液中加入适量Pb(NO3)2溶液将Na2SO4转变成PbSO4,再利用熔融法制备硼硅酸盐玻璃固化体。首次采用在钢铁材料中广泛应用的高温激光共聚焦显微镜原位观察PbSO4在玻璃熔体中的溶解特性,并探究不同温度(800~1 150 ℃)下PbSO4与硼硅酸盐玻璃混合熔制后的热稳定性以及玻璃体中的硫含量。结果表明:在硼硅酸盐玻璃中掺入6%(质量分数,以SO3计)PbSO4的样品在800 ℃和900 ℃为均匀的玻璃陶瓷,其中800 ℃时主要含SiO2及少量BaSO4、PbSO4晶体,900 ℃时SiO2晶体减少,BaSO4晶体增多,PbSO4消失并出现CaMgSi2O6晶体;样品在1 000 ℃时玻璃表面开始出现由PbO、BaSO4、LiNaSO4晶体组成的白色分相,在1 000~1 100 ℃时圆形PbO晶体逐渐长大,BaSO4晶体由块状变为条状;样品在800~1 000 ℃时玻璃体中的硫含量基本保持不变,随着温度进一步升高硫含量迅速下降。 相似文献
7.
以Ce(NO3)3和Na2Mo O4为成膜主盐,乙二胺四乙酸二钠(EDTA-2Na)为配位剂,在碱性条件下对6063铝合金进行化学转化处理。研究了转化液p H、温度和转化时间对Ce–Mo转化膜耐蚀性的影响,得到较优的工艺参数为:Ce(NO3)3·6H2O 6 g/L,Na2Mo O4 8 g/L,EDTA-2Na 4 g/L,尿素18 g/L,Na2CO3 5 g/L,p H 8.5,温度80°C,时间20 min。所得Ce–Mo转化膜呈墨绿色,均匀、致密,主要由Al、Ce和Mo的氧化物组成,耐性硫酸铜点滴时间约为95 s。 相似文献
8.
基于当前对KAl(SO4)2·12H2O蓄热性能研究较少且很少有蓄热装置应用KAl(SO4)2·12H2O作为相变蓄热材料的问题。对KAl(SO4)2·12H2O的制备和蓄热性能进行了总结以及热力学性能分析,得出环境温度及初始温度对相变材料?效率影响较小,终止温度对?效率影响较大;当初始温度为328K,环境温度288K时,最佳终止温度为370K。同时,针对KAl(SO4)2·12H2O应用于移动蓄热装置进行数值模拟,得到液相率、温度随时间的变化曲线。本文研究表明KAl(SO4)2·12H2O是一种性能良好的低温蓄热材料。 相似文献
9.
以Na2S2O3为硫源,采用改进的草酸盐-热解法制备了一系列硫修饰的Co3O4多孔催化剂[Sx@Co3O4,x=0.25、0.50、0.75、1,x为硫的修饰量,以Co(NO3)2·6H2O的物质的量为基准,下同]。以亚甲基蓝(MB)为降解模型,考察了不同催化剂活化过一硫酸盐(PMS)的性能。探讨了催化剂用量、PMS浓度、反应温度、常见阴离子种类在Sx@Co3O4-PMS体系下对MB降解率的影响,并评价了催化剂的循环稳定性。结果表明,随着硫修饰量的增加,Co3O4的催化性能逐渐升高,S1@Co3O4表现出最佳的催化性能。硫元素以SO42– 相似文献
10.
以廉价无机铝盐硫酸铝为原料,氨水为沉淀剂,十二烷基硫酸钠为添加剂,采用简单沉淀法制备得到较大比表面积γ-Al2O3。通过N2低温物理吸附-脱附、X射线衍射、红外光谱、热重、元素分析、扫描及透射电镜等,研究制备过程中沉淀温度、溶液pH值和添加剂用量对产物γ-Al2O3及其前驱体的晶相结构、形貌织构等性质的影响。结果表明,在沉淀温度75 ℃、硫酸铝浓度0.25 mol·L-1、溶液pH=9.0、老化时间12 h和n(十二烷基硫酸钠)∶n[Al2(SO4)3]=0.375∶1条件下,所得前驱体(拟薄水铝石)经600 ℃焙烧后,可获得大比表面积(416.65 m2·g-1)γ-Al2O3,并且样品中因十二烷基硫酸钠添加,引入的S及Na等杂质含量极少。 相似文献
11.
《Fuel Processing Technology》2005,86(4):329-352
Particle and deposit characteristics were studied with a new laboratory-scale deposition–corrosion apparatus designed to simulate the particle formation and deposition in large-scale diesel engines. Synthetic ash particles containing V, Ni, and Na are generated with an ultrasonic nebuliser. Total particle mass concentrations varied from 463 to 1739 mg/N m3 and highest concentrations were reached with SO2(g) feed and cold dilution. Mass size distributions at the size range of 0.01–15 μm (aerodynamic size) were unimodal at 1.4 μm. Particle morphology changed dramatically from 1 to 5 μm sized solid particles without SO2(g) feed into flat wet “pools” with SO2(g) feed. It seemed that condensing sulphuric acid had dissolved the particles. Small 70–90 nm spherical particles were also observed with SO2(g) feed. On the other hand, hardly any S was found in the deposits, which indicated that S as SO2(g)/SO3(g) was transported through the deposit pile into the base material. 相似文献
12.
Binders are generally inorganic, organic or organomineral and have an important influence on the performance and corrosion resistance of slag line and deskulling. Since silicate and phosphate binders have some side effects, in this work sulphate binders such as sulphamic acid, H2NSO3H; aluminum sulphate, Al2(SO4)3; ammonium sulphate, (NH4)2SO4; magnesium sulphate, MgSO4; calcium sulphate, CaSO4; sodium sulphate, Na2SO4; and potassium sulphate, K2SO4, are investigated. Cold crushing strength at different heat treatments of room temperature, 110 °C, 1100 °C, 1400 °C is measured. Apparent porosity of samples without pulp and bulk density together with pH of the binder solution is evaluated and XRD and SEM studies are performed. Among these sulphate binders MgSO4 was found to be the best. It is acidic in nature and develops strong bonds to the basic aggregate, MgO, at low temperatures. At high temperatures it dissociates from MgO(s) and SO3(g) and the remained portion of MgO is the same as host oxide, with no corrosion and easy deskulling. Basic binders such as calcium sulphate, sodium sulphate and potassium sulphate could not strongly bond the MgO aggregates. 相似文献
13.
The scope of this paper includes the development of a modelling approach to predict the ash release behaviour and chemical composition of inorganics during co-firing of coal and biomass. In the present work, an advanced analytical method was developed and introduced to determine the speciation of biomass using pH extraction analysis. Biomass samples considered for the study include wood chips, wood bark and straw. The speciation data was used as an input to the chemical speciation model to predict the behaviour and release of ash. It was found that the main gaseous species formed during the combustion of biomass are KCl, NaCl, K2SO4 and Na2SO4. Calculations of gas-to-particle formation were also carried out to determine the chemical composition of coal and biomass during cooling which takes place in the boiler. It was found that the heterogeneous condensation occurring on heat exchange surfaces of boilers is much more than homogeneous condensation. Preliminary studies of interaction between coal and biomass during ash formation process showed that Al, Si and S elements in coal may have a ‘buffering’ effect on biomass alkali metals, thus reducing the release of alkali–gases which act as precursors to ash deposition and corrosion during co-firing. The results obtained in this work are considered to be valuable and form the basis for accurately determining the ash deposition during co-firing. 相似文献
14.
Byoung-Hwa Lee Sang-In Kim Seung-Mo Kim Dong-Hun Oh Sushil Gupta Chung-Hwan Jeon 《Korean Journal of Chemical Engineering》2016,33(1):147-153
We report a systematic and comprehensive laboratory investigation of the ash deposition behavior of Moolarben (MO) coal, which has recently begun to be imported into Korea. Ash deposition experiments were conducted in a drop tube reactor, and a water-cooled ash deposit probe was inserted into the reactor to affix the ash. The tests were conducted using five types of single coals (two bituminous and three sub-bituminous, including MO coal) and blended coals (bituminous coal blended with sub-bituminous coal). Two indices represent ash deposition behavior: capture efficiency and energy-based growth rate. A thermomechanical analysis evaluated the melting behavior of the resulting ash deposits. The MO coal had the least ash deposition of the single coals due to its high melting temperature, indicated by high ash silica content. Indonesian sub-bituminous coals formed larger ash deposits and were sticky at low temperatures due to relatively high alkali content. However, blends with MO coal had greater ash deposition than blends with other bituminous coals. This non-additive behavior of MO coal blends is likely due to interactions between ash particles. Coals with higher silica content more effectively retain alkali species, resulting in lower melting temperatures and larger ash deposits. Therefore, we recommend that when blending in a boiler, silica-rich coals (SiO2>80%, SiO2/Al2O3> 5) should be blended with relatively low-alkali coals (Na2O+K2O<3%), and the blending ratio of the silica-rich coals indicates less than 10%, which can safely operate the boiler. 相似文献
15.
Mortaga M. Abou-Krisha 《Journal of Coatings Technology and Research》2012,9(6):775-783
An investigation was done on the influences of current density and pH on the electrodeposition behavior of Zn?CNi?CFe alloys using a sulfate bath. The bath consisted of 0.1?M ZnSO4, 0.1?M NiSO4, 0.1?M FeSO4, 0.2?M Na2SO4, 0.2?M H3BO3, and 0.01?M H2SO4. The results of Zn?CNi?CFe alloys?? codeposition revealed that the significant inhibition of Ni and Fe deposition takes place because of the presence of Zn2+ in the plating bath. A transition current density was noticed above wherein a transition from normal to anomalous deposition took place. Bright and uniform surface appearance deposits of Zn?CNi?CFe were the results obtained at pH range 2?C5, and the deposits showed high corrosion resistance. During the investigation, the usage of cyclic voltammetry and galvanostatic techniques for electrodeposition were utilized, while linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Characterization of morphology and the chemical composition of the deposits were performed by means of scanning electron microscopy and atomic absorption spectroscopy. 相似文献
16.
Lucas A. Herweyer Elizabeth J. Opila 《Journal of the American Ceramic Society》2021,104(11):5908-5922
Hi Nicalon, Hi Nicalon S, Sylramic, and Sylramic iBN SiC fibers were exposed to ~60 μg/cm2 of Na2SO4 in a 0.1% SO2/O2 gaseous environment for times between 0.75 and 24 h at 1000°C. After exposure, the corrosion products were characterized using SEM, EDS, ICP-OES, TEM, and EFTEM to determine their high-temperature resistance to Na2SO4 and key reaction mechanisms. All SiC fiber types tested in this work exhibited little resistance to Na2SO4 deposit-induced attack relative to their behavior in dry O2 environments. It was found that Hi-Nicalon displayed the least resistance to Na2SO4 deposit-induced attack due to excess carbon content resulting in the formation of a highly porous crystalline oxide and promotion of basic corrosion conditions. All fiber types formed a crystalline SiO2 reaction product, either cristobalite or tridymite. Sylramic and Sylramic iBN formed a crystalline SiO2 reaction layer containing TiO2 needles due oxidation of TiB2 particles. Additionally, Na2SO4 deposits resulted in pitting of all fiber surfaces. 相似文献
17.
《Ceramics International》2020,46(15):23629-23635
Cr3C2-NiCr/NiCrAlY coating was prepared by high velocity oxygen fuel (HVOF) spraying. The microstructure and the Na2SO4 hot corrosion behavior at different temperatures of the coating were investigated. The Na2SO4 hot corrosion mechanism of Cr3C2-NiCr coating was also discussed. The results showed that HVOF Cr3C2-NiCr coating was relatively dense and mainly composed of Cr3C2, NiCr and a small amount of Cr7C3 three phases. The dense Cr2O3 layer was formed on the surface of Cr3C2-NiCr coating after Na2SO4 corrosion at 750 °C to further prevent corrosion. The coating had produced the obvious longitudinal crack with the increase of hot corrosion temperature up to 900 °C. The corrosion mechanism of Cr3C2-NiCr coating against the Na2SO4 salt at high-temperature was as follows: firstly, the protective oxidizing film was formed at 750 °C, then the protective oxide film dissolved at the interface between the coating and Na2SO4 salt with the hot corrosion temperature increasing up to 900 °C, and subsequently the dissolved anions and cations could migrate to the interface between molten salt and air and the loose and unprotected oxides were regenerated, thereby exacerbating the failure of the coating. 相似文献
18.
《Journal of the European Ceramic Society》2005,25(7):1033-1039
The corrosion behavior of polycrystalline Ti3SiC2 was studied in the mixture of Na2SO4–NaCl melts with various mass ratios at 850 °C. The results demonstrated that Ti3SiC2 suffered from serious hot corrosion attack in the mixture of Na2SO4–NaCl melts when the concentration of Na2SO4 was higher than 35 wt.%. A large amount of corrosion products spalled from specimens during the tests and obvious mass loss was observed. Hot corrosion of Ti3SiC2 would become severe because NaCl had lower melting-point and caused Na2SO4–NaCl mixture melted below 850 °C. However, when the concentration of Na2SO4 was lower than 25 wt.% in the mixture, a protective oxide layer (SiO2 + TiO2) formed on the substrate, the corrosion rate of Ti3SiC2 became quite slow and slight mass gain was observed, the corrosion products did not spall from substrate at 850 °C. The microstructure and phase composition of the corroded samples were investigated by SEM/EDS and XRD. 相似文献
19.
This study aims to elucidate the hot corrosion behavior of Nb-Ti-Si based alloy and its silicide coating in different molten salts at 900?°C. The results show that both K2SO4 and Na2SO4 had detrimental effect on the corrosion performance of the alloy, but almost no effect on the coating. However, NaCl accelerated the corrosion process for both the alloy and coating, showing highest scale thickness and mass gain. The main corrosion products consist mainly of Na or K containing oxides, TiO2 and amorphous silicate. The reactivity of the alloy and the coating in different corrosive environments is discussed. 相似文献