A simulation tool for aerosol formation during sulphuric acid absorption in a gas cleaning process

A simulation tool has been developed to predict sulphuric acid aerosol formation in typical industrial absorption processes for gas cleaning. The underlying model comprises homogeneous nucleation and the growth of a polydisperse droplet collective under the special circumstances of a gas–liquid contact device where heat and mass transfer processes between the bulk phases take place simultaneously. The model is applied to a hot flue gas (200 °C) with sulphuric acid concentrations between 5 and 100 mg m⁻³ (STP) (STP: standard temperature and pressure). The simulation yields high droplet number concentrations up to 10¹⁶ m⁻³ especially for low gas inlet concentrations of sulphuric acid (5 mg m⁻³ (STP)), and very small droplet sizes in the range 20–100 nm. The droplet number concentrations decrease and the droplet sizes increase with increasing sulphuric acid inlet concentrations. It is shown that small droplets (<20 nm) need relatively high supersaturation for growing. If the saturation in the absorption equipment is not high enough the droplets partially re-evaporate but do not vanish due to the extremely low vapor pressure of concentrated sulphuric acid. The resulting size distributions of the aerosol droplets are not very sensitive with respect to the nucleation model used. This is demonstrated by comparing nucleation models with and without hydrate formation. The new simulation tool allows an estimate of the true sulphuric acid removal efficiency of absorption processes which is often not more than 50% due to aerosol formation. In general, the simulation results enable a deeper insight in the mechanisms of aerosol formation and behavior in absorption processes.     

硫酸技术的新发展

介绍了近几年硫酸系统设备结构的改进,废热利用率的提高,催化剂性能的改善,生产装置开工率的提高以及低浓度二氧化硫气体处理技术的发展等硫酸生产技术的发展情况。     

硫酸厂转化工序管道热补偿设计

介绍了转化工序管道热补偿设计中有关的计算,不锈钢波纹补偿器的特点,新型的长拉杆－复式补偿器组合结构以及补偿器预变形安装和管道支撑的支座形式。     

磷钼酸在硫酸-醋酸体系中对304不锈钢的缓蚀性能研究

考察了磷钼酸在硫酸一醋酸混酸介质中对304不锈钢的缓蚀性能,对缓蚀机理进行了初步推断。实验结果表明,磷钼酸是一种阳极型缓蚀剂,在ω(H2SO4)=0．5％～1．5％、ω(CH3COOH)=58．0％、ω(HPA)=0．1％～0．2％,温度100～120℃的条件下,腐蚀速度小于0．05mm／a,缓蚀率高迭99．7％。     

硫磺与硫酸市场分析与展望

介绍了全球和中国硫磺、硫酸生产、消费及需求情况。2012年全球硫磺需求量56500kt,供应总量53200kt;硫酸贸易量16500kt。2012年中国硫资源（以S计）表观消费量约30000kt,其中硫磺约14000kt;2012年中国硫酸表观消费量约85000kt,主要用于磷肥、钛白粉、氢氟酸、己内酰胺、粘胶纤维等生产。由于硫酸产能过剩、需求不旺引发的市场低迷仍将持续,预计未来2—3年中国硫磺和硫酸市场难有大的改观。     

热管技术在硫酸工业废热回收中的应用

介绍分离套管式热管蒸汽发生系统的结构特点。由于产汽系统与工艺气体完全隔离,满足了硫酸生产的工艺要求。几则应用实例表明,运行可靠,操作简单,维修方便。     

硫酸用不锈钢研究发展综述

对硫酸用不锈钢的发展过程进行全面综述。重点介绍各种含氮奥氏体——铁素体双相不锈钢、高钼含氮奥氏体不锈钢、高硅不锈钢、微量贵金属元素改性不锈钢的化学成分、力学性能、耐腐蚀性能和应用范围。用氮、硅等元素代替贵重合金元素．开发出性能优越而价格低廉的新型不锈钢,是今后的发展方向。     

Aerosol formation in gas-liquid contact devices—nucleation, growth and particle dynamics

In gas-liquid contact devices like absorbers, scrubbers, quench coolers or condensers, aerosols can be formed by spontaneous phase transitions, initiated by homogeneous or heterogeneous nucleation, if special process operation conditions lead to a metastable, i.e. a supersaturated state in the gas phase. Aerosol formation can impact severely the mass separation efficiency of gas-liquid contactors. This is demonstrated by experiments performed in semi-technical plants.The paper is aimed to identify strategies for understanding and describing the complex aerosol behaviour in gas-liquid contact devices.Operation conditions are identified under which supersaturation can arise, and the fundamentals of modelling aerosol formation and growth in gas-liquid contactors are discussed.The SENECA code developed by the authors allows to simulate aerosol formation and behaviour in contact devices as well as in multistage gas cleaning processes. Experimental results show that most of all important features of aerosol behaviour in flue gas cleaning and in condensation processes can be predicted with good accuracy by SENECA.     

80kt／a硫磺制酸装置的设计改进意见

对1995--1996年期间设计的4套80kt／a硫磺制酸装置的试运行情况进行总结。总体来说,装置的工艺流程选取和设计是成功的：SO2转化率达到99．5％-99．7％,硫酸产量高于270t／d,尾气排放浓度符合国家标准。主要存在的问题是：原料硫磺酸度高、水含量大,造成熔硫过程稀酸腐蚀严重;柴油升温将大量水蒸汽带入转化系统,烟气通入后产生酸冷凝腐蚀;废热回收设备的用材和结构形式不理想,出现较严重的外漏和内漏现象。针对问题提出了改进意见。     

采用先进技术和可靠设备保证硫酸装置长期稳定生产

通过介绍国外先进的主鼓风机、浓硫酸循环泵、不锈钢转化器、不锈钢热器、纤维除雾器和催化剂的特点及使用情况,表明采用先进技术和可靠设备是保证硫酸装置长期稳定生产的关键。     

硫化氢湿式催化法制硫酸工艺在焦炉煤气精制系统中的应用

在焦炉煤气净化过程中,结合采用湿式催化法由Ｈ２Ｓ生产ｗ（Ｈ２ＳＯ４）＝７８％的硫酸。介绍了工艺流程、控制参数以及生产过程中的改进。     

Purification and utilisation of iron-contaminated sulphuric acid

The purification and utilisation of sulphuric acid contaminated with iron is discussed in detail. It is found that treatment of the acid with FeSO₄·7H₂O resulted in complete removal of the iron impurity. Partial removal of the iron was affected by treatment with acetone and ammonium sulphate. Treatment with activated carbon was not found to be effective. The study shows that the contaminated sulphuric acid can be utilised to prepare sodium sulphate and calcium sulphate.     

Evaluation of non-toxic corrosion inhibitors for copper in sulphuric acid

The aim of this paper is to study influence of the molecular structure on the inhibiting properties of organic compounds in corrosion processes in acid media. The inhibiting efficiency of non-toxic imidazole derivatives on copper corrosion in sulphuric acid is investigated. The investigation is performed using electrochemical methods of potentiodynamic polarisation as well as gravimetric measurements. The results of the investigation show that the inhibiting properties of substituted imidazoles depend on molecular structure. The best protection (93%) is obtained by adding a phenyl ring to the imidazole structure. The values of standard free energies of adsorption, as calculated from the Freundlich isotherm, indicate that in the presence of sulphuric acid imidazole derivatives adsorb on copper by a physisorption-based mechanism.     

Influence of chelating agents on the tribocorrosion of tungsten in sulphuric acid solution

The corrosion and tribocorrosion of tungsten in 0.01 M H₂SO₄, without and with the presence of lactic acid and phosphoric acid as chelating agents was studied here.The passive behaviour was characterised using potentiostatic polarization and potential step techniques combined with rotating disk electrodes. Surface analysis techniques (XPS, AES) were used to assess surface chemistry. The tribocorrosion of tungsten was investigated using a tribometer equipped with an electrochemical cell operating at applied passive potentials of 0.2 V and 1.0 V.Under static corrosion conditions chelating agents were found to enhance passive film dissolution and to decrease the passive film thickness. Despite this, the effect of the investigated chelating agents was limited under tribocorrosion conditions. Indeed, only lactic acid at the most anodic potential lead to significant differences in material removal by impeding the formation of protective tungsten oxide tribolayers. The discrepancy on the effect of chelating agents in corrosion and tribocorrosion was explained in terms of the different involved time constants.     

A numerical investigation of aerosol dynamics in a wall-less reactor

This paper describes a numerical investigation of aerosol formation during silane decomposition in a wall-less reactor. The wall-less reactor is amenable to numerical investigation because the homogeneous chemical reactions leading to the formation of solid particles are isolated from heterogeneous effects, such as occur at the walls of a laminar flow aerosol reactor. The flow/heat transfer and gas-phase chemical kinetics are simulated utilizing separate one-way coupled models. The aerosol dynamics model is based on a simplified sectional model originally developed by Okuyama et al. This model is modified to allow for the simulation of particle growth via condensation. Simulations have been performed which indicate that particle growth via condensation may be an important process. Additionally, the effects of total reactor pressure, temperature and inlet silane concentration on the dynamics of the aerosol population have been investigated. Conditions which result in the formation of larger and more numerous particles have been identified.     

300 kt/a硫磺制酸废热锅炉的制造

３００ｋｔ／ａ硫磺制酸废热锅炉由３部分组成,第一部分置于焚硫炉后,为单汽包横向冲刷式强制循环水管锅炉;第二部分置于转化器一段出口,为垂直烟道横向冲刷式蒸汽过热炉;第三部分置于转化器四段出口,为垂直烟道横向冲刷式低温过热炉,３个部共用１个汽包,生产３．８２ＭＰａ,４５０℃中压过热蒸汽。另外,介绍了废热锅炉材料选择、制作及质量控制。     

Inhibiting properties and adsorption of some thioamides on mild steel in sulphuric acid solutions

The inhibiting properties and adsorption behaviour of thioacetamide (TAA), thiobenzamide (TBA) and thiocinnamamide (TCA) on mild steel in sulphuric acid solution were studied by gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. TBA and TCA were found to be mixed type inhibitors providing good corrosion inhibition. Different mechanisms of adsorption and corrosion inhibition were observed for the tested thioamides. In the cases of TBA and TCA, the adsorption of the compounds is chemical and the values of the activation energy (Ea) and the pre-exponential factor (A) are lower than the corresponding values observed in inhibitor free solution. The adsorption of TAA is physical and the values of Ea and А are higher than the corresponding values in sulphuric acid solution. The adsorption process of TBA and TCA on the mild steel/sulphuric acid solution interface is described by Langmuir’s isotherm. A correlation between the adsorption capability and the inhibiting efficiency of the molecules and their donor–acceptor properties (E _HOMO and E _LUMO) has been established. It is ascertained that the protection effect of TAA depends on the amount of hydrolysis products.     

Some phthalazin derivatives as non toxic corrosion inhibitors for copper in sulphuric acid

Phthalazin derivatives were tested as corrosion inhibitors of copper in 1 M H₂SO₄ using electrochemical polarization and weight loss techniques. This study monitored the evolution of the inhibitory effect of the phthalazin derivatives, according to their substituents. A significant decrease in the corrosion rate of copper was observed in the presence of the investigated inhibitors. The inhibition efficiency (%I) increases with increasing inhibitor concentration. The potentiodynamic polarization data indicated that, the inhibitors were of mixed type, but the cathodic effect is more pronounced. The slopes of the cathodic and anodic Tafel lines are approximately constant and independent on the inhibitor concentration. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors. The adsorption on the copper surface follows the Langmuir isotherm model.     

大型硫磺制酸装置中风机安全保护的设计

介绍了大型硫磺制酸装置中空气鼓风机安全保护系统的设计方法。鼓风机的测量信号能同时满足DCS以及就地仪表盘的要求。该系统具备正常启动、安全保护及仪表显示和故障报警等功能。     

钼冶炼烟气配气制酸装置的运行情况

介绍了金堆城钼业股份有限公司一期200 kt/a钼冶炼烟气配硫铁矿焙烧气制酸装置的主要工序及运行情况。投产以来,转化率达99.83%以上,吸收率在99.99%以上,排放尾气SO_2质量分数不超过439 mg/m~3。并且针对装置运行中存在的一些问题,对生产工艺和设备进行了改进和优化。