EXPERIMENTAL STUDIES OF DEPOSITION RATES IN THE PRESENCE OF ALKALI SULFATE VAPOR SCAVENGING BY SUBMICRON PARTICLES IN COMBUSTION GAS BOUNDARY LAYERS†

We examine the mass transfer consequences of the nonequilibrium scavenging of condensible vapor (Na₂SO₄) by suspended solid particles (MgO) within combustion gas boundary layers (BLs) using an extension of our 'flash-evaporation' technique (Rosner and Liang, 1986) and laser light scattering methods. In contrast to the result of introducing additives which form miscible condensates with the primary alkali sulfate on a sufficiently cold deposition target—a situation which leads to vapor deposition rate increases (Liang and Rosner, 1986), additives which form nonvolatile, submicron particles in the main-stream, capable of scavenging the alkali vapor(s), reduce total alkali deposition rates at all levels. This result indicates that the thermophoretic diffusivity of such 'getter' particles is smaller than the Fick diffusivity of the scavenged alkali sulfate vapor. Both nonequilibrium laminar BL-theory (Castillo and Rosner, 1987) and our flash evaporation-light scattering experiments reveal that the alkali mass transfer rate reduction factor correlates with the product N_pr_p²—a quantity proportional to the scavenging particle cloud external surface area per unit volume. These results also imply that, in practice, finely divided inorganic sulfur getters, present in the 'fire-side' boundary layer at sufficiently high number densities, would also suppress the total deposition rate of alkali compounds on heat exchanger surfaces.     

Effect of alkalies on portland cement hydration II. Alkalies present in form of sulphates

Alkalies present in cement in the form of Na₂SO₄ and/or K₂SO₄ do not alter the progress of C₃S and C₃A hydration. The setting time becomes accelerated especially with K₂SO₄ due to the formation of syngenite CaSO₄·K₂SO₄·H₂O. The compressive strength is lowered significantly.     

燃煤锅炉烟气中Na2SO4生成的化学动力学研究

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。     

四元体系Na+,K+//Br-,SO42——H2O373K相平衡

采用等温溶解平衡法研究了四元体系Na⁺,K⁺//Br^-,SO₄^2--H₂O在373 K条件下的相平衡关系,测定了平衡溶液的溶解度和密度,并根据实验数据绘制相应的相图、水图和密度图。研究发现:交互四元体系Na⁺,K⁺//Br^-,SO₄^2--H₂O在373 K温度下,有复盐钾芒硝Na₂SO₄·3K₂SO₄生成,相图由3个共饱和点、7条单变量曲线和5个结晶区组成。其中,5个结晶区分别对应单盐:K₂SO₄,KBr,NaBr,Na₂SO₄和复盐Na₂SO₄·3K₂SO₄(Gla)。     

Fluxing reactions of sulphate and carbonates in cement clinkering. I. Systems CaSO4-K2SO4 and K2SO4-CaCO3

Phase equilibria and thermodynamics have been used to determine compatabilities in the systems CaSO₄-K₂SO₄ and K₂SO₄-CaCO₃. In the CaSO₄-K₂SO₄ system, a polymorphic inversion at 200°C is encountered in K₂Ca₂(SO₄)₃. Thermodynamic calculation of the reciprocal salt system K₂SO₄-CaCO₃-CaSO₄-K₂CO₃ discloses that the join K₂SO₄-CaCO₃ constitutes a stable binary: experiments in flowing CO₂ at 1 bar pressure confirm this. A noteworthy feature of the system is the solid solution of CaCO₃ in K₂SO₄, reaching 20% mol % CaCO₃. The eutectic, located at 880°C and 43 mol % CaCO₃, is attainable without significant decomposition. The possible consequences to clinkering reactions are discussed.     

SIMPLIFIED DEWPOINT PREDICTIONS FOR N-TRACE SALT-CONTAINING NON-IDEAL CONDENSATES IN HIGH TEMPERATURE REACTIVE VAPOR ENVIRONMENTS

Accurate predictions of dewpoint temperatures in multi-trace salt-containing high temperature reactive environments are complicated by two common phenomena. First, the reactive environment promotes the formation of vapor precursors other than the 'parent' condensate salts (due to dissociation and reaction among the combustion products). Second, the salt condensate solutions that form are usually thermodynamically non-ideal even though the coexisting multi-species vapor is, frequently, ideal. As an extension of our recent treatment of the simpler (limiting) case of a binary non-ideal solution, we present here a computational procedure that makes the general N-component case tractable and illustrate its implementation for the case of a ternary (alkali sulfate) condensate system. To account for the multiplicity of vapor phase species we again rely on an 'effective (single component) vapor pressure' for each 'component' salt to permit simple calculations for the salt solution dew point. The required single salt vapor/liquid equilibrium data are here generated using a thermochemical equilibrium (free-energy minimization) code. When recast as an 'equivalent' vapor pressure correlation, this information is then used to solve the multisalt dewpoint problem by satisfying the requirements of vapor/condensate equilibrium with a multi-component non-ideal condensate solution. As an illustrative (ternary) case, using the principles outlined above, we carry out calculations for the prototypical system: K₂S0₄/Na₂S0₄/Li₂S0₄.     

硫酸钠/氧化硅复合定形相变材料的溶胶凝胶法制备和表征简

A sodium sulfate （NaeSO4）/silica （SiO2） composite was prepared as a shape-stabilized solid-liquid phase change material by a sol-gel procedure using Na2SiO3 as the silica source. Na2SO4 in the composite acts as a latent heat storage substance for solid-liquid phase change, while SiO2 acts as a support material to provide structural strength and prevent leakage of melted NazSO4. The microstructure and composition of the prepared composite were characterized by the N2 adsorption, transmission electron microscope （TEM）, scanning electron microscope （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray diffraction. The results show that the prepared Na2SOJSiO2 composite is a nanostructured hybrid of NazSO4 and SiO2 without new substances produced during the phase change. The macroscopic shape of the NazSO4/SiO2 composite after the melting and freezing cycles does not change and there is no leakage of Na2SO4. Determined by differential scanning calorimeter （DSC） analysis, the values of phase change latent heat of melting and freezing of the prepared NazSO4/SiO2 （50%, by mass） composite are 82.3 kJ.kg i and 83.7 kJ.kg-1, and temperatures of melting and freezing are 886.0 ℃ and 880.6 ℃, respectively. Furthermore, the Na2SOJSiO2 composite maintains good thermal energy storage and release ability even after 100 cycles of melting and freezing. The satisfactory thermal storage performance renders this composite a versatile tool for high-temperature thermal energy storage.     

三元体系K +,Cs +//SO4 2——H2O 298.2 K稳定相平衡研究

采用等温溶解法开展了三元体系K ⁺,Cs ⁺//SO₄ ^2--H₂O 298.2 K稳定相平衡研究,测定了该体系溶解度、密度及折光率。结果表明,该三元体系在298.2 K下属于复杂体系,有固溶体（K,Cs）₂SO₄产生,且固溶体相区最大;其稳定相图包含3条单变量曲线、3个析出相区和2个共饱点;共饱点处对应的液相组成分别为w（K₂SO₄）=11.69%、w（Cs₂SO₄）=4.02%和w（K₂SO₄）=3.39%、w（Cs₂SO₄）=60.84%。平衡液相的密度和折光率随Cs₂SO₄含量的增大呈现递增的趋势。采用经验公式对平衡液相的折光率进行理论计算,计算值和实验值具有良好的一致性。     

煤化工烟道气毒性成分对Chlorella pyrenoidosa生长和细胞成分的影响

探究煤化工烟道气中毒性成分对微藻的影响是利用微藻固定煤化工烟道气CO₂实现减排的关键。本文利用不同浓度的NaHS、Na₂SO₃和NH₃·H₂O培养Chlorella pyrenoidosa（C. pyrenoidosa）,以探究煤化工烟道气主要毒性成分H₂S、SO₂和NH₃气体水溶物的毒性。实验结果表明：NaHS、Na₂SO₃和NH₃·H₂O浓度分别低于1mmol/(L·d)、40mmol/(L·d)和7mmol/(L·d)时对C. pyrenoidosa生长无抑制作用,而且Na₂SO₃[＜40mmol/(L·d)]会显著促进 C. pyrenoidosa的生长;NaHS 添加4mmol/(L·d)时会在生长初期抑制C. pyrenoidosa的生长,NH₃·H₂O添加35mmol/(L·d)则会直接造成藻细胞的破碎死亡。与对照组相比,NaHS和Na₂SO₃浓度分别低于1mmol/(L·d)、10mmol/(L·d)时对C. pyrenoidosa的细胞成分无影响;NaHS添加4mmol/(L·d)使藻蛋白含量提高7.13%;Na₂SO₃添加40mmol/(L·d)使藻蛋白降低13.45%,总糖含量提高42.90%;NH₃·H₂O的添加会使藻蛋白含量降低,总糖含量提高。微藻生物质整体蛋白质含量较高,可作为蛋白饲料来源。研究结果表明,C. pyrenoidosa对煤化工烟道气中的主要毒性气体有较好的耐受性,利用煤化工烟道气培养微藻具有可行性。     

-15℃下Na+, K+, Mg2+// Cl-, SO4-2-H2O体系相平衡

采用等温溶解平衡法,研究了Na⁺, K⁺, Mg²⁺//Cl^-, SO₄^-2-H₂O, 五元水盐体系在-15℃下NaCl·2H₂O饱和时的相平衡关系,测定了溶解度和密度,并绘制出相应的相图。研究结果表明:该五元体系平衡相图中有3个四盐共饱点,7条单变量溶解度曲线及5个两盐结晶区,5个两盐结晶区分别对应于KCl+NaCl·2H₂O、Na₂SO₄·10H₂O+ NaCl·2H₂O、MgSO₄·7H₂O+NaCl·2H₂O、MgCl₂·8H₂O+NaCl·2H₂O、KCl·MgCl₂·6H₂O+ NaCl·2H₂O;所 得-15℃相图和25℃下相图相比,相图结构大为简化:K₂SO₄·MgSO₄·4H₂O、KCl·MgSO₄·3H₂O、Na₂SO₄·3K₂SO₄、Na₂SO₄·MgSO₄·4H₂O、MgSO₄·(4～6)H₂O、K₂SO₄·MgSO₄·6H₂O结晶区均消失,Na₂SO₄结晶区转变为Na₂SO₄·10H₂O且结晶区扩大,KCl、MgSO₄·7H₂O、KCl·MgCl₂·6H₂O结晶区缩小,MgCl₂·6H₂O结晶区转变为MgCl₂·8H₂O。在此基础上研究了不同组成的盐湖卤水在降温过程中的结晶规律,为低温盐田工艺的开发提供了理论依据。     

Na2SO4掺杂含MgO铝酸钙熟料的结构表征及浸出性能

使用分析纯MgO、CaCO₃、SiO₂、Al₂O₃与Na₂SO₄在1350℃保温1 h合成了掺杂Na₂SO₄的含MgO铝酸钙熟料,在Na₂CO₃溶液体系下研究了其氧化铝浸出性能,通过XRD等分析手段对其晶体结构和自粉化性能进行了研究。结果表明,Na₂SO₄可以显著提升铝酸钙熟料的浸出性能,Na₂SO₄掺杂量由0%提高到4%,熟料的氧化铝浸出率由61.89%提高到92.01%,继续添加Na₂SO₄,浸出性能趋于稳定。由XRD结果可知,Na₂SO₄促使20CaO·13Al₂O₃·3MgO·3SiO₂（Q相）发生分解并使其转变为12CaO·7Al₂O₃（C₁₂A₇）。Na⁺进入C₁₂A₇晶格引起晶格畸变,从而提高C₁₂A₇的氧化铝浸出性能。Na₂SO₄的加入降低了熟料的自粉化性能,Na₂SO₄掺杂量由0%提高到6%,熟料的自粉率由97.46%下降到85.34%,当Na₂SO₄掺杂量达到10%后,熟料自粉率仅为36.3%。     

硫酸盐熔融反应法从钛铁矿中提取钛的研究

以海南万宁的钛铁矿和硫酸铵为主要原料,通过熔融反应法使钛铁矿中的钛转化为易溶于稀酸的硫酸氧钛,用稀硫酸浸取,达到提高钛浸取率的目的。考察了硫酸铵加入量、焦硫酸钾加入量、反应温度、稀硫酸浸取浓度对钛浸取率的影响。实验结果表明：硫酸铵和焦硫酸钾的加入量、反应温度对钛浸取率的影响较大。提高钛浸取率的最佳条件为：m（钛铁矿）∶m（硫酸铵）∶m（焦硫酸钾）=1∶6∶0.5,反应温度为450 ℃,保温时间为30 min,稀硫酸浸取浓度为2.32 mol/L,在此条件下钛的浸取率达到96.82%。     

N-Zn/TiO2光催化氧化脱硫废液中亚硫酸钠的研究

采用溶胶凝胶法合成了氮、锌共掺杂二氧化钛催化剂（N-Zn/TiO₂）,用于催化氧化双碱法脱硫废液中的亚硫酸钠。通过X射线衍射、红外光谱、X射线光电子能谱和场发射环境扫描电镜对N-Zn/TiO₂催化剂的形貌和结构进行了表征。并考察了催化剂用量、溶液pH、空气流量、亚硫酸钠初始浓度对N-Zn/TiO₂光催化氧化亚硫酸钠的影响。实验结果表明：在不加N-Zn/TiO₂催化剂的情况下,将脱硫废液中的亚硫酸钠完全氧化需要8 h,而N-Zn/TiO₂在紫外光照射下能在1.5 h内将亚硫酸钠催化氧化完全。催化剂的用量对反应速率的影响最大,废液中亚硫酸钠的氧化速率随着催化剂用量的增多呈上升趋势。其次是溶液的pH对亚硫酸钠的氧化有较大影响,随着pH的增大,亚硫酸钠的氧化速率呈先增大后减小的趋势。实验所得到的最优反应条件为：催化剂用量为m（催化剂）/m（亚硫酸钠）=1/100,pH=6.5,空气流量为4 L/min。     

The effect of temperature on phase equilibria of polyethylene glycol (PEG8000)-K2SO4-H2O at T=(288.15, 298.15, 308.15) K

The phase behavior of potassium sulfate (K₂SO₄) in polyethylene glycol with molecular weight 8000 (PEG8000) and water (H₂O) mixed solvent at 288.15, 298.15, and 308.15 K were determined. According to the results, when the temperature are 288.15 and 298.15 K, there is only a solid-liquid phase equilibrium relationship in the system, and the phase diagrams are both divided into three parts which respectively are the regions of unsaturated homogeneous liquid (L), one liquid and one solid K₂SO₄ (L + S) and one liquid and two solids K₂SO₄ and PEG8000 (L + 2S). The solubility of K₂SO₄ in PEG8000-H₂O mixed solvent decreased with the addition of the PEG8000 in the solution. Comparing the diagrams of 288.15 and 298.15 K, the sizes of regions of (L) and (L + S) increased and that of (L + 2S) decreased with the increase of temperature. While at 308.15 K, solid-liquid and liquid-liquid equilibrium coexist, and there are six parts in the complete phase diagram at 308.15 K, adding the areas of one liquid and one solid K₂SO₄ (L + S), two liquids (2 L), two liquids and one solid K₂SO₄ (2 L + S). The equations developed by Merchuk, Hu, and Jayapal were used to fit the binodal curves data of the system at 308.15 K, meanwhile, the experimental tie-line data of the system at 308.15 K were correlated by Othmer-Tobias equation and Bancroft equation.     

模拟城市垃圾焚烧中硫化合物对重金属Cd迁移分布的影响

The effect of sulfur compounds （including sulfur, sulfide, sulfite and sulfate）, initial concentration of heavy metal and operating conditions on Cd emission in municipal solid waste （MSW） incineration were investi-gated using a simulated tubular furnace and simulated MSW spiked with Cd. The concentration of Cd was meas-ured by inductively coupled plasma-atomic emission spectrometry （ICP-AES） after digesting the samples including bottom ash, fly ash and flue gas according to related USEPA methods. The results show that S and Na2S tend to in- crease Cd partitioning in bottom ash, whereas Na2SO3 and Na2SO4 tend to reduce Cd partitioning in bottom ash. The effect of sulfur compounds on Cd partitioning in bottom ash was in the sequence of Na2S〉S〉Na2SO3〉 Na2SO4. chemical equilibrium analysis is also performed to determine the effect of sorbents on Cd adsorption. The calculations show that S presents strong affinity for Cd and restrains Cd adsorption by SiO2, whereas when temperature rises to between 830℃ and 1030℃, Cd adsorption efficiency of SiO2 is over 80% and the efficiency of Al2O3 is up to 85%.     

Selective oxidation of toluene on V2O5/TiO2/SiO2 catalysts modified with Te, Al, Mg, and K2SO4

The effect of the modification of vanadia catalysts supported on TiO₂/SiO₂ by the oxides of Al, Mg and Te, and K₂SO₄on the selective oxidation of toluene in the vapor phase has been studied. The catalysts were prepared by successive impregnation and characterized by BET surface measurements, XRD, XPS, and TPR. Addition of the second component decreased specific activity in all cases, except Al, mainly due to the decrease of surface area. Intrinsic activity was increased with addition of Te and Al, and decreased by that of Mg, while K₂SO₄ had little effect. These differences could be explained by the observed changes in either vanadium surface dispersion or reducibility. Selectivity to benzaldehyde increased markedly with addition of Te or K₂SO₄, that caused the formation of new oxide phases, V₃Ti₆O₁₇ and TiV₂O₆, in which vanadium is in a partially reduced state.     

常见钠盐的高温挥发特性及热解机理

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NaCl、Na₂CO₃及Na₂SO₄的挥发特性进行热力学计算。结果表明,在N₂气氛中,NaCl在达到熔点后以气态NaCl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N₂气氛。     

Some experimental observations of aerosol formation in the photo-oxidation of sulphur dioxide

The formation of particles in the u.v. photolysis of ppm concentrations of SO₂ in pure nitrogen and in nitrogen-oxygen mixtures has been studied in a flow system. Both the number of particles and the mass of the H₂SO₄ aerosol produced was determined over a range of SO₂ and water vapour concentrations.

In the near u.v. (λ = 290–400nm) the mass conversion of SO₂ to H₂SO₄ was too small to be measured, but particles were detected on a condensation nucleus counter above a threshold SO₂ concentration when the H₂SO₄ formation rate was sufficient to achieve an appreciable nucleation rate. The number of stable particles formed increased with water vapour concentration at a given H₂SO₄ production rate. These experimental data agree reasonably well with recent theoretical calculations of aerosol nucleation and growth rate in the H₂SO₄/H₂O system.

At short wavelengths (λ = 185 nm) a much higher H₂SO₄ formation rate was achieved. Although nucleation occurred at < 1 per cent r.h. the aerosol growth process was slow at low water vapour concentrations. A r.h. of 30 per cent was required for the incorporation of the bulk of the H₂SO₄ into the aerosol phase.     

GO/Al2O3复合纳滤膜的制备及其稳定性能研究

以平均孔径为20 nm的Al₂O₃管式超滤膜为载体,经多巴胺改性后,利用压力驱动沉积法成功制备出能在水溶液中长期稳定的GO/Al₂O₃复合纳滤膜,并通过改变负载量实现了对GO层厚的调控。结果表明,随错流时间的延长,不同GO负载量下GO/Al₂O₃复合纳滤膜的纯水渗透系数均呈现先降低后稳定的趋势。且随着GO负载量的增加,稳态纯水渗透系数逐渐降低;当GO负载量增加到90 mg/m²后,GO/Al₂O₃复合纳滤膜对一二价盐的渗透系数与截留率均无显著变化。同时,由于盐测试过程中残余的盐离子在GO片层间产生了交联作用,从而导致随着在纯水中存放时间的延长,不同GO负载量的GO/Al₂O₃复合纳滤膜对一二价盐的截留率均呈上升趋势。GO负载量为140 mg/m²的GO/Al₂O₃复合纳滤膜在水中浸泡680 h后对1 mmol/L Na₂SO₄的截留率可达到91.0%。GO/Al₂O₃复合纳滤膜对四种一二价盐的截留率满足：R(Na₂SO₄) > R(MgSO₄) > R(NaCl) > R(MgCl₂)。