共查询到19条相似文献,搜索用时 156 毫秒
1.
为揭示O 2/CO 2燃烧过程中高浓度的CO对煤焦异相还原NO的影响,在1073 K温度下使用山西褐煤在卧式炉上进行了实验。分别对O 2/CO 2浓度比及CO浓度下NO的还原特性进行详细实验研究。研究结果表明:在O 2/CO 2气氛下,O 2浓度为30%时具有较高的还原率;相同O 2浓度下O 2/CO 2气氛较空气气氛NO还原率高,表明在CO存在的条件下,高浓度的CO 2会促进NO的还原;当CO浓度从1.5%逐渐升高时,NO的还原率逐渐降低,到CO浓度为5%时,NO还原率比没有加入CO时还要低,而在空气气氛下CO浓度的变化对NO的还原率影响较小。 相似文献
2.
本文通过实验研究了CO 2质量分数为11.39%~70.95%,壁面过冷度为5~25 K,总压力为5~15 kPa的CO 2/H 2O混合气体自然对流条件下在水平管外的凝结换热规律,结果表明CO 2/H 2O的凝结换热系数随CO 2含量和壁面过冷度的增大而降低,但随总压力的增大而增大。根据实验结果建立了新关联式,将关联式应用到凝汽器的设计计算与分析,且对凝汽器进行了分离特性和经济性分析。 相似文献
3.
利用分子动力学(MD)模拟方法研究整体煤气化联合循环(IGCC)合成气(CO 2/H 2)水合物法分离CO 2的分离机理,系统研究了CO 2水合物、H 2水合物以及合成气水合物法一级分离所得CO 2/H 2混合气体水合物的微观结构及性质.模拟分析 n个CO 2或H 2与水合物笼状结构的整体结合能Δ E关键词:
水合物法分离
分子动力学模拟
整体煤气化联合循环合成气
2分离')" href="#">CO2分离 相似文献
4.
将可调谐半导体激光吸收光谱技术应用于高温气体浓度在线检测,谱线参数的准确性非常重要。为利用红外波段进行燃烧生成H 2O的浓度在线测量,需要实验校准H 2O的谱线参数,尤其是Ar加宽系数,该系数对燃烧反应速率测量和机理验证至关重要。采用半导体激光器作为光源,结合实验室搭建的谱线参数测量系统,采集了1.39 μm波段附近H 2O的4条吸收谱线信号,获得了谱线线强、自加宽系数和N 2加宽系数,与HITRAN数据库和文献结果进行了对比,均吻合较好。首次系统地获得了该波段谱线的Ar加宽系数。在谱线参数确定基础上,获得了在反射激波高温条件下H 2/O 2/Ar燃烧生成H 2O的浓度随时间的演变曲线,验证了相应燃烧动力学机理。结果为利用该波段进行含氢燃料燃烧过程H 2O浓度测量及相关高温燃烧动力学研究提供了可靠的实验依据。 相似文献
5.
将低钠煤(H-煤)和高钠煤(Na-煤)分别在沉降炉中进行制焦实验,研究了钠对焦样的孔隙结构、碳微晶结构以及反应性的影响。研究表明,煤中钠含量增加后,在N 2气氛下,非灰基质失重率V *会下降;而在CO 2气氛下,V *却会升高。煤焦的碳化学有序度IG/I All与V *具有关联性,在有Na的催化时,其与反应性的关联性被破坏。焦的反应性主要由焦的孔隙结构和焦中Na的含量来确定,在动力控制区,Na的催化作用是引起焦反应性发生改变的主要因素。 相似文献
6.
利用密度泛函理论研究了0.25单层(ML),0.5ML,0.75ML和1ML吸附率下H 2O在SrTiO 3-(001)TiO 2表面上的吸附行为.比较了不同吸附率下分子吸附和解离吸附的稳定性,利用微动弹性带(nudged elastic band)方法计算了H 2O的解离势垒.结果表明:在低吸附率(0.25ML和0.5ML)时,H 2O表现为解离吸附;在0.75ML吸附率下,分子吸附和解离吸附同时存在;而在全吸附(吸附率为1ML)时,分子吸附更稳定.基于对H 2O分子与表面之间以及H 2O分子之间的电荷转移和相互作用的分析,讨论了吸附率对H 2O吸附和解离的影响.
关键词:
2O')" href="#">H 2O
吸附
3-(001)TiO 2表面')" href="#">SrTiO 3-(001)TiO 2表面
密度泛函理论 相似文献
7.
采用广义梯度密度泛函理论的改进Perdew-Burke-Ernzerh方法结合周期性层晶模型,研究了CO 2分子在Pu(100)面上的吸附和解离.吸附能和几何构型的计算表明,CO 2以穴位C4O4构型吸附最为有利,吸附能为1.48 eV.布居分析和态密度分析表明,CO 2与Pu表面相互作用的本质主要是CO 2分子的杂化轨道2 πμ与Pu5f,Pu6d,Pu7s轨道通过强电子转移和弱重叠杂化的方式相互作用而生成了新的化学键.计算的CO 2→CO+O解离能垒为0.66 eV,解离吸附能为2.65 eV, 表明在一定热激活条件下CO 2分子倾向于发生解离性吸附.O 2,H 2,CO和CO 2在Pu (100)面吸附的比较分析表明,较低温度下的吸附强度顺序依次为O 2,CO,CO 2,H 2;较高温度下的吸附强度顺序依次为O 2,CO 2,CO,H 2.
关键词:
密度泛函理论
Pu (100)
2')" href="#">CO 2
吸附和解离 相似文献
8.
相比常规烟气气氛中的选择性催化剂还原脱硝(SCR)反应,商用钒钛(V 2O 5/TiO 2)催化剂在NO 2加入后构成的快速SCR反应气氛中具备优异的低温脱硝反应性能,快速SCR反应被认为具有良好的低温脱硝应用前景。烟气中存在的水蒸气会严重降低SCR催化剂在低温下的脱硝活性,因此本文重点研究了水蒸气对钒钛催化剂上标准及快速SCR反应的影响,发现快速SCR反应比标准SCR反应具备更优异的抗水性能。本文采用动力学实验结合密度泛函理论计算的研究方法,得到H 2O和NH 3在催化剂表面的竞争性吸附是H 2O抑制标准SCR反应的重要影响因素之一,而在快速SCR反应中,NO 2对催化剂的快速重氧化作用使得反应速率始终保持在较高水平,削弱了H 2O对NH 3的竞争性吸附影响,从而了展现良好的抗H 2O影响性能。 相似文献
9.
基于多体展式方法所导出的SiH 2( X1A1)分析势能函数,用准经典的Monte Carlo轨线法研究了Si( 1Dg)+H 2(0,0)和H( 2Sg)+SiH(0,0)的原子与分子反应动力学过程.研究结果表明:Si( 1Dg)与H 2(0,0)的碰撞在低能时(小于209.20 kJ/mol)生成稳定的络合物SiH 2( X1A1),该反应是无阈能反应;而H( 2Sg)与SiH (0,0)碰撞不能生成稳定的络合物,主要发生交换反应H( 2Sg)+SiH (0,0)→Si( 1Dg)+H 2(0,0),该反应也是无阈能反应.
关键词:
2')" href="#">SiH 2
势能函数
反应截面
轨线 相似文献
10.
利用电喷雾质谱(ESI-MS)和紫外-可见吸收光谱(UV-Vis)分析,研究了CrCl 3·6H 2O 浓度为0.1~0.6 mol·L-1的水溶液和[1ChCl∶2EG]/CrCl 3·6H 2O ILs中,Cr(Ⅲ)配合物的存在形式。研究结果表明,在含有CrCl 3·6H 2O的溶液中,Cr(Ⅲ)与Cl-和H 2O形成[Cr(H 2O) nCl 6-n] n-3配合物,其配合物的优势物种受CrCl 3·6H 2O浓度的影响。水溶液中Cr(Ⅲ) 的优势配合物为[Cr(H 2O) 6]3+与[Cr(H 2O) 5Cl]2+,并随CrCl 3·6H 2O浓度增加,水溶液的UV-Vis吸收光谱峰红移,[Cr(H 2O) 5Cl]2+的相对含量增加。而[1ChCl∶2EG]/CrCl 3·6H 2O ILs中的优势配合物为[Cr(H 2O) 2Cl 4]-和[Cr(H 2O) 3Cl 3],且随CrCl 3·6H 2O 浓度增加,溶液的颜色从浅橙红色逐渐变为深绿色,溶液的UV-Vis吸收光谱峰蓝移,[Cr(H 2O) 3Cl 3]的相对量增加。说明CrCl 3·6H 2O的浓度变化,将影响配体Cl-和H 2O与Cr(Ⅲ)配位结合的配位数,从而影响配合物优势物种的相对量。 相似文献
11.
本文用X射线和差热分析方法对BaO-Li 2O-B 2O 3三元系中的两个截面:BaB 2O 4-Li 2B 2O 4和BaB 2O 4-Li 2O作了研究。在BaB 2O 4-Li 2B 2O 4赝二元系中发现了一个新的化合物4BaB 2O 4·Li 2B 2O 4。化合物在930±3℃由包晶反应形成,并与Li 2B 2O 4形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol%Li 2B 2O 4。在BaB 2O 4-Li 2O截面中也存在化合物4BaB 2O 4·Li 2B 2O 4,其包晶反应温度从930±3℃随Li 2O含量增加下降到908±3℃。在组分60mol%Li 2O处形成另一个新的化合物2BaB 2O 4·3Li 2O。该化合物在630±3℃也是由包晶反应形成,并与Li 2O和Li 2CO 3分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB 2O 4-Li 2B 2O 4和BaB 2O 4-Li 2O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB 2O 4·Li 2B 2O 4和2BaB 2O 4·3Li 2O的X射线粉末衍射图案进行了指标化,其结果:4BaB 2O 4·Li 2B 2O 4的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB 2O 4·3Li 2O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。
关键词: 相似文献
13.
The reaction of CO 2 and H 2O to form bicarbonate (HCO −3) was examined on the nearly perfect and vacuum annealed surfaces of TiO 2(110) with temperature programmed desorption (TPD), static secondary ion mass spectrometry (SSIMS) and high resolution electron energy loss spectrometry (HREELS). The vacuum annealed TiO 2(110) surface possesses oxygen vacancy sites that are manifested in electronic EELS by a loss feature at 0.75 V. These oxygen vacancy sites bind CO 2 only slightly more strongly (TPD peak at 166 K) than do the five-coordinated Ti 4+ sites (TPD peak at 137 K) typical of the nearly perfect TiO 2(110) surface. Vibrational HREELS indicates that CO 2 is linearly bound at the latter sites with a νa(OCO) frequency similar to the gas phase value. In contrast, oxygen vacancies dissociate H 2O to bridging OH groups which recombine to liberate H 2O in TPD at 490 K. No evidence for a reaction between CO 2 and H 2O is detected on the nearly perfect surface. In sequentially dosed experiments on the vacuum annealed surface at 110 K, CO 2 adsorption is blocked by the presence of preadsorbed H 2O, adsorbed CO 2 is displaced by postdosed H 2O, and there is little or no evidence for bicarbonate formation in either case. However, when CO 2 and H 2O are simultaneously dosed, a new CO 2 TPD state is observed at 213 K, and the 166 K state associated with CO 2 at the vacancies is absent. SSIMS was used to tentatively assign the 213 K CO 2 TPD state to a bicarbonate species. The 213 K CO 2 TPD state is not formed if the vacancy sites are filled with OH groups prior to simultaneous CO 2+H 2O exposure. Sticking coefficient measurements suggest that CO 2 adsorption at 110 K is precursor-mediated, as is known to be the case for H 2O adsorption on TiO 2(110). A model explaining the circumstances under which the proposed bicarbonate species is formed involves the surface catalyzed conversion of a precursor-bound H 2O–CO 2 van der Waals complex to carbonic acid, which then reacts at unoccupied oxygen vacancies to generate bicarbonate, but falls apart to CO 2 and H 2O in the absence of these sites. This model is consistent with the conditions under which bicarbonate is formed on powdered TiO 2, and is similar to the mechanism by which water catalyzes carbonic acid formation in aqueous solution. 相似文献
14.
采用熔融淬冷法制备了新型的Er 3+/RE 3+(RE 3+=Ce 3+,Tb 3+)掺杂的GeO 2-TeO 2-Na 2O玻璃。测试了样品的差示扫描分析曲线、可见/近红外透过率、拉曼光谱、吸收光谱和1.53 μm发光光谱。研究发现适量的TeO 2对GeO 2的取代提高了玻璃的热稳定性,缩短了样品的吸收截止边。拉曼分析表明该系统玻璃有着宽广的红外透过范围。同时研究了980 nm激发下稀土离子(RE 3+=Ce 3+,Tb 3+)的加入对Er 3+掺杂的45GeO 2-45TeO 2-10Na 2O玻璃的光谱性能和能量传递的影响。发现随着Ce 3+浓度增加大大地提高了1.53 μm的发光强度,CeO 2的最佳掺杂摩尔分数为0.1%,而Tb 3+的共掺降低了1.53 μm的发光强度。可见Er 3+/Ce 3+掺杂的45GeO 2-45TeO 2-10Na 2O玻璃在C波段光纤放大器方面有潜在的应用前景。 相似文献
15.
A new procedure for the preparation of Tl 2Ba 2CaCu 2O 8-δ is presented. In the first step stoichiometric amounts of Cu(NO 3) 2·3H 2O, Ba(OH) 2·H 2O, CaO and Tl 2O 3 are reacted in a closed alumina crucible at 760°C to form a mixture of Tl- 2212, CuO, CaO and other oxide phases. In the second step this material is milled, pelletized and fired in a gold-sealed alumina crucible at 860–900°C for three to eight hours. Three batches of Tl-2212 prepared by this method were investigated showing less than 1% loss of thallium while Tc was close to 110 K. Rietveld refinements using time-of-flight neutron-diffraction data demonstrate that the method produces pure material in a reproducible way and that the materials are substoichiometric with respect to oxygen (δ=0.3). Investigations using electron diffraction and high-resolution electron microscopy indicate the absence of stacking faults. 相似文献
16.
The solid–solid interactions between cobalt and ferric oxides to produce CoFe 2O 4 were followed up using XRD investigation. The effect of Li 2O-doping on the ferrite formation was also studied. The electrical and dielectric parameters of pure and doped mixed solids precalcined at 1273 K were measured using d.c and a.c instruments.The dopant concentration was varied between 0.5 and 6 mol% Li 2O. The results obtained revealed that Li 2O doping much enhanced the ferrite formation due to an increase in the mobility of the reacting species. The addition of the smallest amount of Li2O (0.5 mol%) resulted in measurable variations in the electrical constants (ρ, Ea, ′, ″ and tan δ). Resistivity increased upon increasing the dopant concentration up to 1.5 mol% exceeding the values measured for the undoped sample. Furthermore, the presence of 6 mol% Li2O brought about a significant decrease of electrical resistivity. Also, the activation energy decreased with increasing the dopant concentration. The dielectric constant behaves according to ε=const. 1/ρ1/2. The Li2O-doping modified the values of different dielectric constants, the change in these constants was found to be strongly dependent on the amount of Li2O added.These results have been discussed in terms of the potentiality of Li2O in increasing the mobility of the reacting species involved in the ferrite formation. 相似文献
17.
Zirconium oxide (ZrO 2) is one of the leading candidates to replace silicon oxide (SiO 2) as the gate dielectric for future generation metal-oxide-semiconductor (MOS) based nanoelectronic devices. Experimental studies have shown that a 1–3 monolayer SiO 2 film between the high permittivity metal oxide and the substrate silicon is needed to minimize electrical degradation. This study uses density functional theory (DFT) to investigate the initial growth reactions of ZrO 2 on hydroxylated SiO 2 by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl 4) and water (H 2O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl 4 with the hydroxylated SiO 2 surface was studied. Upon adsorption, ZrCl 4 forms a stable intermediate complex with the surface SiO 2–OH * site, followed by formation of SiO 2–O–Zr–Cl * surface sites and HCl. For the second half-reaction, reaction of H 2O on SiO 2–O–Zr–Cl * surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl atom from the surface site and an H atom from H 2O. The results reveal that the stable intermediate complexes formed in both half-reactions can lead to a slow film growth rate unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half-reactions are similar to those of ZrO 2 ALD on ZrO 2 and as well as the energetics of ZrO 2 ALD on hydroxylated silicon. The energetics of the growth reactions with two surface hydroxyl sites are also described. 相似文献
18.
以Li 2CO 3粉末为原料,采用一种冷冻干燥湿法工艺,制备出综合性能较好的Li 2O陶瓷小球。通过研究冷冻成形、煅烧、分解和烧结等工艺过程,优化了Li 2O陶瓷小球的制备工艺,并对获得的Li 2O陶瓷小球进行了性能表征。结果表明:冷冻成形制备的凝胶小球在650 ℃煅烧后可得到纯净的Li 2CO 3小球,再于真空条件下多步程序升温至720 ℃可制得主要相为Li 2O的小球,小球尺寸分布均匀,直径约为0.8 mm,平均晶粒尺寸为9 μm,于900 ℃高温烧结后小球的密度可达理论密度的69.5%。 相似文献
19.
We report a successful crystal growth of Ca 2Y 2Cu 5O 10 and anisotropic behavior of magnetic susceptibility associated with an antiferromagnetic phase transition. Single crystals were obtained by the floating-zone method using an infrared radiation furnace. Composition and structural characterization shows that the grown crystals are qualified for physical measurements. The magnetic susceptibility along each crystallographic axis shows a typical behavior of antiferromagnetic phase transition at TN=31 K, and the ordered magnetic moments are found to lie along the b-axis. 相似文献
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