Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler

The purpose of this work was to study different ways to mitigate alkali-related problems during combustion of biomass in circulating fluidized beds. Wood chips and wood pellets were fired together with straw pellets, while the tendency to agglomerate and form deposits was monitored. In addition to a reference case, a number of countermeasures were applied in related tests. Those were addition of elemental sulphur, ammonium sulphate and kaolin to a bed of silica sand, as well as use of olivine sand and blast-furnace slag as alternative bed materials. The agglomeration temperature, composition and structure of bed-ash samples were examined. The flue-gas composition, including gaseous alkali chlorides, was measured in the hot flue gases and in the stack. Particles in the flue gas were collected and analysed for size distribution and composition. Deposits were collected on a probe in hot flue gases and their amount and composition were analysed. Addition of kaolin was found to be the best method to counteract the agglomeration problem. The deposition problem is effectively counteracted with addition of ammonium sulphate, while kaolin is too expensive to be used commercially against deposits, and sulphur is less effective than ammonium sulphate.     

Crystal Size Measurement: Comparison of the Techniques of Sieving and Coulter Counter

Carefully sieved crystals of nickel ammonium sulphate are analysed with a Coulter particle size counter. Simple correction factors are proposed to rationalize the two sizing techniques.     

Reducing Agglomeration of Ammonium Perchlorate Using Activated Charcoal

Ammonium perchlorate is the most widely employed oxidizer for composite solid propellants. When exposed to atmosphere, it absorbs moisture and agglomerates. It is usually vacuum dried in order to avoid this agglomeration. When ammonium perchlorate that has been exposed to atmosphere for a certain period of time, is used in making a composite solid propellant, the burning rate is different because of the change in particle size distribution due to its agglomeration. This change in burning rate will change the thrust‐time profile from that of what it is designed for. As one goes to a finer ammonium perchlorate particle size this problem becomes more evident. Experimental studies aimed at reducing the agglomeration of ammonium perchlorate by coating it with activated charcoal. Ammonium perchlorate coated with 1 % activated charcoal showed almost no agglomeration, even when the particle size of ammonium perchlorate is approx. 1 μm. The burning rates also remained unchanged when ammonium perchlorate coated with 1 % activated charcoal was employed in propellant composition, after it has been exposed to the atmosphere for a period of 1 h.     

从氨浸电镀污泥产物中氢还原分离铜、镍、锌的研究

本研究采用湿法氢还原对电镀污泥氨浸产物中的铜、镍、锌等有价金属进行了分离回收．对氨浸产物进行焙烧、酸溶处理后，在硫酸铵体系弱酸性溶液中氢还原分离出铜粉，然后在氨性溶液中氢还原提取镍粉，最后沉淀回收氢还原尾液中的锌．有价金属的回收率达到98～99％．本文提出的流程简单，设备投资少，在工业生产及环境保护方面有较广的应用前景．     

硫酸铵体系氢还原工艺中的杂质积累

通过考察硫酸铵体系氢还原生产镍复合材料的流程，探讨了金属杂质在体系中的积累情况．结果表明，在生产循环过程中，体系中杂质含量的积累存在一极限值，控制还原料液的纯度及还原尾液的利用率可以有效控制产品质量．文中提出的杂质离子积累模式为类似的氢还原流程设计提供了借鉴．     

采用粒数衡算模型研究沉淀过程中粒子的聚结和破裂

通过采用MSMPR反应沉淀器,研究了普鲁卡因青霉素反应沉淀过程中粒子的聚结和破裂对过程的影响机理,并对用生死函数表征聚结和破裂的粒数衡算模型采用新的分析方法。结果表明,将二元破裂模型应用于该粒数衡算模型是可行的。     

采用粒数衡算模型研究沉淀过程中粒子的聚结和破裂

通过采用MSMPR反应沉淀器,研究了普鲁卡因青霉素反应沉淀过程中粒子的聚结和破裂对过程的影响机理,并对用生死函数表征聚结和破裂的粒数衡算模型采用新的分析方法。结果表明,将二元破裂模型应用于该粒数衡算模型是可行的。     

Alumina trihydrate crystallization. Part 2. A model of agglomeration

In the second part of this paper on the kinetics of crystallization of aluminum trihydroxide from caustic aluminate solutions, interest is specially focused on the analysis of crystal size distribution as a function of time, in an isothermal batch crystallizer. Breakdown and agglomeration are shown to affect these curves simultaneously. While only qualitative information on breakdown was obtained, agglomeration could be isolated experimentally. Its rate was measured and fitted to a kinetic model which pictures agglomeration as the result of binary collisions between particles.     

Processing of oxidized nickel ores with ammonium chloride

A method for processing nickel ores with ammonium chloride is considered. The results of thermodynamic calculations for the reactions of the oxide components of nickel ore with ammonium chloride are given. Thermogravimetric and kinetic investigations were performed. The technological sequence of the separation of oxidized nickel ores into individual oxides was developed.     

我厂复混肥生产中产生结疤的原因及解决措施

以尿素、磷铵、过磷酸钙、硫酸钾等原料用团粒法生产复混肥的过程中，烘干机、斗提机、卧式双辊链条粉碎机常产生结疤，分析产生结疤的原因是物料含水分和游离酸过高所致，并提出相应解决措施。     

Electroreductlon of cyclohexanone oxime

An electrochemical method for preparing cyclohexylamine from cyclohexanone oxime has been developed. Cyclohexanone oxime underwent smooth reduction in an aqueous ethanolic ammonium sulphate medium on nickel black deposited on graphite. The oxime is not reducible at ordinary copper or nickel electrodes. Nickel black deposited on copper or nickel was also found to be ineffective due to poor adhesion of the nickel black.     

Generation of bimodal metal dispersion in faujasite X

Bimodal nickel dispersions are prepared by the reduction of nickel ion-exchanged NaX using a mixture of hydrogen and carbon monoxide. Bimodal platinum dispersions are obtained by the temperature programmed reduction of platinum tetrammine ion-exchanged NaX. The occurence of bimodal dispersions exhibiting particles of supercage size as well as particles exceeding this dimension requires lattice fragmentation, i.e. the presence of protons and water, and the possibility for initial agglomeration by collisions with high sticking probabilities.     

Jet-pump crystallizers in reaction-crystallization processes with solid reagent–barium sulphate precipitation study

The research results concerning barium sulphate precipitation from the concentrated water solutions of barium chloride by means of crystalline ammonium sulphate addition are presented. The experiments were carried out in a continuous laboratory DTM crystallizer with inner circulation of suspension. A liquid jet-pump device generating ascending/descending flow of medium in a mixing chamber was used. Influences of barium chloride concentration in a feed solution (5–24 mass%), process temperature (303–348 K), mean residence time of suspension in a crystallizer working volume (600–10,800 s) and direction of circulation in jet-pump's mixing chamber on the resulting crystal size distribution of barium sulphate were investigated. Neural network models of the process were elaborated, providing the basis for the theoretical analysis of the influence of hydrodynamic regime on the population density distributions of crystal product. Conformity of the simulated population density distribution data with the experimental ones, as well as with the SDG kinetic model predictions was analyzed, verified and discussed.     

Sonochemical synthesis of LaMnO3 nano-powder

We report the preparation of LaMnO₃ nanosized powder by the sonochemical process. Sodium dodecyl sulphate (SDS) was used as surfactant, to prevent agglomeration. The particle size obtained in this method was 19–55 nm. The phase formation temperature of LaMnO₃ was 700 °C which is lower than other conventional processes. So sonochemical process is cost effective and it is more acceptable considering its ease of preparation in comparison to other conventional processes. Powder synthesized was characterized by measuring crystallite size, specific surface area, morphology and by thermal analysis. The particle sizes of the powders were controlled by calcinations schedule. Narrow size distribution and core and shell structure of the prepared powder was revealed by transmission electron microscopy.     

铝材表面化学镀镍技术

在常规铝材化学镀镍工艺基础上，提出一种在酸性化学镀镍前增加一道碱性化学预镀镍工艺的铝材表面化学镀镍新技术。介绍了其预镀镍的工艺流程与操作要点。研制了一种中等浓度的含镍、铁的多元合金浸锌液，并通过正交实验得出了浸锌最佳方案，确定了碱性化学预镀镍的最佳配方：25g／L硫酸镍，25g/L次磷酸钠，30g／L柠檬酸三钠，10g／L焦磷酸钠，10-15mL／L三乙醇胺，30g/L氯化铵。弯曲试验表明，镀镍层与铝基体结合强度很高；镀镍层SEM照片显示，镀镍层晶粒尺寸大小均匀，各晶粒间结合紧密，孔隙率低，耐腐蚀能力强。     

硫酸亚铁制硫酸钾的研究

以硫酸亚铁,氯化钾和碳酸氢铵为原料制取硫酸钾,同时副产氧化铁红和氧化铵,反应条件温和,操作简单,原料综合利用好,经济效益可观。     

液相共沉淀法制备氧化铟锡超细粉体材料的研究进展

介绍了液相共沉淀法制备氧化锢超细锡粉体材料的工艺,分析了沉淀剂、反应物的浓度、煅烧的温度和时间、分散剂等四个因素对制备过程及产物的影响。按照三氧化铟和二氧化锡的质量比为9∶1选用铟盐和锡盐；用氨水、尿素或碳酸铵作沉淀剂,并且沉淀剂不同,反应时应控制的pH值和反应时间也不同；反应物In~(3+)的浓度0．2mol／L时可得到接近纳米级的超细氧化铟锡粉体材料；700～800℃煅烧3～5h,可使前驱物成为球状,其团聚现象也可以得到综合平衡；分散剂为硫酸铵、硅烷偶联剂KH570等,对其分散机理作了简要的分析。     

Uniform precipitation of Yttria-Stabilized zirconia

An experiment on precipitation of zirconia by urea, urotropin, and ammonium hydroxide precipitants is described. The morphological and phase composition of the precipitated powders are investigated. It is shown that a buffer has a positive effect on reducing the agglomeration. The agglomeration factor for the ammonium hydroxide precipitant is reduced from 175 to 40. A powder consisting of soft agglomerates having a developed surface and easily disintegrated in milling to a size of < 1 µm is obtained. Individual particles are 0.06–0.08 µm in size.Translated from Ogneupory, No. 6, pp. 2–5, June, 1995.The work has been supported by the Fund for Fundamental Investigations of the Russian Academy of Sciences.     

Electroreduction of phenyl cyanide and benzyl cyanide on nickel cathode

An electrochemical method for preparation of primary amines from organic cyanides using nickel black deposited over graphite substrate as cathode has been studied. It has been observed that it is possible to reduce benzyl cyanide both in ethanolic sulphuric acid and in aqueous ethanolic ammonium sulphate media. But with phenyl cyanide, the reduction is efficient only in ethanolic sulphuric acid medium. Both in laboratory and 75 A scale experiments 62–66% yield has been obtained at a current efficiency of 36–44% for benzylamine. Similarly a yield ranging from 60–80% with a current efficiency of 36–52% has been obtained for β-phenylethylamine both in laboratory scale and also in large scale experiments. Results of operation of a 500 A cell for the preparation of β-phenylethylamine are also presented.     

Effect of crystallisation on the reaction kinetics of nickel reduction by hydrogen

The reaction kinetics of precipitation from aqueous solution is not only a function of the concentration of reagents but also depends on the properties of the solid particles formed in the process. These property changes arise from the increasing influence of surface properties in comparison to volumetric bulk-properties as the particle size decreases. The ratio α of the active surface area to the actual surface area of the particles in the system is used in this work to evaluate the reaction activity of the particles. The investigation of the reaction kinetics of nickel reduction without sampling during the process of the reaction was successfully carried out in the experiment. The overall kinetics of nickel reduction have been suggested, where the constants relate to the main processes of nickel precipitation from the solution. The significant agglomeration reduces the deactivation of the nickel particles in the precipitation process, while breakage and crystal growth decrease the activation. The activations of dry and wet seeds are insignificantly different.