氨合成催化剂内表面利用率计算模型的研究

针对目前氨合成催化剂内表面利用率计算模型所存在的问题，本文提出一种基于径向基函数网络并结合主成分回归方法的网络模型。试验结果证明，该模型用于氨合成催化剂内表面利用率效果良好。     

碱法合成甲醇钠的热力学分析

氢氧化钠溶解在甲醇中与甲醇反应是制取甲醇钠的主要方法,文中针对该液相反应建立热力学循环,计算了298 K下反应的标准摩尔吉布斯自由能变和标准摩尔焓变,将范特霍夫方程积分后得到化学平衡常数随温度的变化关系式。计算结果表明:该反应的标准摩尔吉布斯自由能变略大于0,说明反应在常温下难以自发进行,需要不断移出生成的水来提高反应转化率;反应微放热,化学平衡常数随温度升高将变小,得到的化学平衡常数与温度的关系式与文献报道的实验结果基本一致,可为工业模拟提供理论计算依据。根据化学平衡常数关系式和汽液平衡模型对生产过程进行分析计算,获得了较适宜的反应温度范围。     

氨合成催化剂内表面利用率一种新的计算模型

运用径向基函数网络结合偏最小二乘回归（RBF－PLSR）的方法建立了氨合成催化剂内表面利用率计算模型，并对模型进行了验证，结果表明，该模型计算精度高，具有一定的实用价值。     

氨合成最大反应速率模型及计算

建立了计算最佳温度下的氨合成最大反应速率模型,提出了模型的数值解方法;以三套管冷管并流式氨合成塔为例,分别绘制了氨合成反应速率与氨摩尔分率、转化率和反应温度的关系曲线,并与实际反应曲线进行了比较,结果表明,本文所绘制的曲线不仅可以直观地反映氨合成最大反应速率随氨摩尔分率(或转化率)和反应温度变化的动力学规律,而且可以表示出催化剂床层内实际反应速率与最大反应速率的偏离程度。     

尿素合成的化工计算——动力学模型篇

根据尿素合成的第一步反应--甲铵生成反应的活化能,得出该反应是一个飞速反应.由微分方程式推导了一个尿素合成的第二步反应--甲铵脱水反应的动力学积分方程式,同时由文献数据导得了其反应速度常数的两个计算模型.应用本动力学模型,可计算稳态流动的工业尿塔任何时间段内液态甲铵转化为尿素的生成率,同时还用该模型计算了尿素合成反应所需的反应时间.     

甲醇合成化学平衡常数的测定与推算

以低压法(5MPa)甲醇合成为背景,建立了气相法甲醇合成化学平衡常数的实验测定系统,测定了不同温度和压力下,CO、CO_2同时加H_2合成CH_3OH反应的平衡组成及化学平衡常数K_p,同时以实验结果为依据,对K_p的理论推算进行了探讨,其中对文献中计算以逸度表示的平衡常数K_f的各种方程进行了比较。结果表明,基于Cherednichenko的K_(f,Ⅰ)和Bissett的K_(f,Ⅱ),采用修正的SRK方程,对K_p的推算取得了满意的结果。     

尿素合成的化工计算——热力学模型篇

通过热力学分析和体系简化,分别用PHS状态方程和实验活度系数模型来修正气液两相的非理想行为,以文献报道的实验数据为基础,建立了一个尿素合成反应过程中半经验半理论的热力学模型.该模型的计算值与实验数据和文献数据较一致,可用于尿素合成反应进程中、达化学平衡及高压分解时的气液平衡计算.     

甲醇合成化学平衡常数的测定与推算

以低压法(5MPa)甲醇合成为背景,建立了气相法甲醇合成化学平衡常数的实验测定系统,测定了不同温度和压力下,CO、CO_2同时加H_2合成CH_3OH反应的平衡组成及化学平衡常数K_p,同时以实验结果为依据,对K_p的理论推算进行了探讨,其中对文献中计算以逸度表示的平衡常数K_f的各种方程进行了比较。结果表明,基于Cherednichenko的K_(f,Ⅰ)和Bissett的K_(f,Ⅱ),采用修正的SRK方程,对K_p的推算取得了满意的结果。     

常用氨合成催化剂的反应速率常数和最佳活性使用温度

根据常用的6种氨合成催化剂的本征活性测定数据，用焦姆金动力学方程回归得到反应速率常数与温度的关系。利用所得反应速率常数，模拟了这6种氨合成催化剂在中型氮肥厂φ1000mm三套管氨合成塔的反应结果。从催化剂的使用温度来看，从A106、A109、A110－1、A110－2、ICI74－1到ZA－5最佳活性使用温度不断降低。     

石油烃热裂解反应速率常数估算方法的研究进展

石油烃热裂解反应动力学模型是工业裂解炉的核心技术之一。建立具有广泛适用性的石油烃热裂解自由基机理模型，需要获得构建该模型反应网络中各个基元反应的反应速率常数，综述了包括线性自由能关系、估算活化能的非线性方程、反应速率和分子特征量关系以及部分依赖实验确定反应速率的4类文献中报道过的估算反应速率常数的方法，并结合石油烃热裂解反应机理模型的需求，认为裂解机理模型中的反应可根据分类的不同，选取其中合适的方法进行反应速率常数的估算。     

运用人工神经元网络建立氨溶解度计算模型

本文运用RBF－PCR方法建立氨溶液度计算模型，试验结果表明，该模型用于氨溶解度的计算，效果良好。     

轴径向型氨合成塔的数学模型及工艺优化研究

运用氨合成化学反应本征动力学方程,建立了轴径向型氨合成塔拟均相一维的催化床层内氨浓度和反应温度分布的数学模型。利用正常生产运行的操作数据反算得到了各段催化床层的催化剂活性系数;逐一对单元工艺操作条件进行了优化,模拟计算出系统压力随氨合成塔工艺操作条件变化的情况,从中确定出一组工艺操作条件的优化值;通过实际生产运行,对优化前后氨合成塔工艺操作数据进行了对比,结果实明,生产操作工况良好。     

尿素醇解法合成氨基甲酸甲酯平衡常数的测定

文章测定了尿素醇解法合成氨基甲酸甲酯的平衡常数。在433.15K时,无催化剂条件下,甲醇和尿素在高压釜内反应生成氨基甲酸甲酯,待反应达到平衡后,通过气相色谱仪和液相色谱仪测定平衡混合物的组成来计算反应的平衡常数。气相可近似认为是氨气和甲醇组成的二元混合物,液相近似认为是尿素、甲醇和氨基甲酸甲酯组成的三元混合物。实验结果表明,实验重现性较好,平衡常数数值是可靠的。     

Prediction of the chemical equilibrium constant for peracetic acid formation by hydrogen peroxide

An expression for temperature dependence of the chemical equilibrium constant for peracetic acid synthesis from acetic acid and hydrogen peroxide in an aqueous solution, derived on the basis of the van't Hoff and Kirchhoff equations, was proposed. The reverse trend of the chemical equilibrium constant vs. temperature was apparent when the predicted values of the constant were compared with experimental ones taken from the literature. However, using the proposed model to calculate the chemical equilibrium constant resulted in better prediction of the equilibrium composition for peracetic acid synthesis at 297.5 K than using experimental data from the literature.     

ⅢJD3500型低压低阻氨合成系统研究设计及应用实践

研究以氨合成化学反应平衡曲线、最适宜温度曲线获得最高氨净值为目标,通过优化反应器结构及工艺流程,设计了ⅢJD3500型DN2 500 mm三层四段氨合成塔及配套流程.在原料气中甲烷含量、循环气中甲烷含量均高的实际工况下,该系统产氨能力达900 t/d左右,系统压力≤18 MPa,系统阻力≤1.2 MPa,氨合成塔阻力≤...     

化学链合成氨技术研究进展及展望

氨气不仅是重要的化工原料和良好的氢载体,其可以作为无碳燃料的属性也引起了广泛关注。低能耗高效率的合成氨工艺是实现氨作为燃料应用的关键。阐述了合成氨工艺的发展历程,概述了以Haber-Bosch工艺为基础的多相催化和光、电等外场力驱动的合成氨工艺的新发展,重点介绍了化学链合成氨的最新研究成果,并对其研究方向进行展望。传统Haber-Bosch工艺苛刻的反应条件以及热力学和动力学之间的矛盾,促使科研工作者一直努力探索可持续的环境友好型合成氨技术。随着催化科学和表面科学的进步,人们对合成氨的反应机理和催化剂的物化性质有了更深入的认识,这为开发“绿色”合成氨工艺提供了有价值的参考信息,如要提高过渡金属催化合成氨性能,须尽量规避表面物种吸附能间的线性关系。另外,以可再生能源为能量来源的光、电催化合成氨,借助外场作用可以有效影响反应速率和机理。化学链技术的发展为合成氨工艺提供了新思路,将合成氨过程解耦为吸氮和释氮产氨2个或多个分步反应,可较好地缓解合成氨热力学和动力学矛盾,规避反应物竞争吸附。同时,各分步反应可分别优化,使整个化学链合成氨工艺达到最佳反应效果。未来采用太阳能聚热供能以及以生物质炭为碳源,并对化学链合成氨工艺进行经济性分析反馈指导工艺流程的优化,可降低碳基化学链制氨工艺的成本和能耗。     

Preliminary synthesis of work exchange networks

In many chemical plants such as LNG, refineries, air enrichment, and ammonia compression is a major consumer of energy. In such plants, some process streams may need compression, while others may need expansion. Optimal integration of these streams may yield major savings in energy. In this work, we introduce a work exchanger network synthesis problem that is analogous to the well-known heat exchange network synthesis problem. We model the details of compressor and turbine operating curves to identify high-pressure and low-pressure streams that should be matched for work exchange via compression/turbine stages located on a single shaft. We propose a superstructure for the work exchange network configuration and develop a mixed-integer nonlinear program (MINLP) to minimize the total annualized cost for a constant speed of the single shaft. We use this preliminary model to optimize shaft speed, and demonstrate the benefits of an optimized network via an illustrative case study.     

Neues Verfahren zur Methanol- und Ammoniak-Synthese. Der Gas/Feststoff/Feststoff-Rieselströmungsreaktor – ein neuer Reaktortyp zur Führung chemischer Gleichgewichtsprozesse

New process for the production of methanol and ammonia. The gas/solids/solids thrickle flow reactor – a new kind of reactor for chemical equilibrium processes . A new process for the production of ammonia or methanol has been developed in the high pressure laboratory of Twente Technical University. The reactants can be made to react completely in a single reactor pass, thus avoiding expensive recirculation. Complete reaction without recirculation is accomplished by a combination of two reversible processes: a chemical reaction and a selective adsorption of the reaction product on a solid in constant flow. On introduction of an inert-gas free stoichiometric mixture of reactants into the reactor, the exhaust gas outlet can be closed. If there is an excess of one of the reactants or of inert gas, it can leave from the top of the reactor. Such a process has been accomplished in a new gas/solids/solids trickle flow reactor in which a granulated adsorbent ?rains”? through a fixed bed of catalyst. The present article describes the use of this kind of reactor for methanol synthesis. Considerable savings in production costs are expected relative to the modern Lurgi low pressure process. A pilot plant is to be built to characterize and evaluate the new process. Royal Dutch Shell has registered a patent application.     

Back Extraction of HCl from TOA Dissolved in N-Octanol by Aqueous Ammonia in a Microchannel Device

To recover the extractant in the preparation of KH₂PO₄ using the extraction method, studies for the back extraction of HCl by aqueous ammonia from TOA (trioctylamine) dissolved in n-octanol were conducted. First, the reaction of HCl back extraction from TOA in n-octanol with aqueous ammonia was examined in shaking flasks and the equilibrium of this reaction was validated. The equilibrium constant of the stripping reaction was determined in the temperature range of 297.7-318.2 K and the reaction enthalpy was found to be -17.8 kJ/mol indicating that the stripping reaction was exothermic. Then kinetic experiments were performed in a microchannel device with the elimination of mass transfer limitations, as demonstrated by the experimental results. A kinetic model was established to obtain the forward and backward interfacial reaction rate constants with the help of the obtained equilibrium constant of the stripping reaction. This model described the measured data well and predicted correctly the change of HCl concentration in the oil phase along with the residence time in our experiments. Furthermore, the activation energy for the forward (8.21 kJ/mol) and backward (26.0 kJ/mol) reaction was determined and subsequently the forward and backward interfacial reaction rate constants were determined in the temperature range of 298.7-313.2 K.     

Enhanced ammonia synthesis in multifunctional reactor with in situ adsorption

A steady-state, one-dimensional mathematical model for a multifunctional reactor with in situ adsorption for ammonia synthesis is developed. The model represents integrated ammonia catalytic equilibrium reaction with ammonia adsorption in a co-current gas-flowing solids-fixed bed reactor (GFSFBR). The model was used for simulating the performance of an industrial-scale reactor, which confirmed that the reactant conversion is significantly higher in the multifunctional reactor in comparison to the conventional reactor under optimal conditions. The analysis of the simulation results shows that the conversion in the GFSFBR stays higher than those in the classical reactor even if much lower temperatures and pressures are used.