物料在输送管道中的流动状态研究

散状固体物料在气力输送管道内的流动是极其复杂的，每种物料都有其独特的流动特征。通过分析散状固体物料在输送管道内的运动状态，可为正确选择输送参数和设计气力输送系统提供依据。     

Using a boundary line approach to analyze N2O flux data from agricultural soils

Predicting the N₂O flux from soils is difficult because of the complex interplay of the various processes involved. In this study a boundary line approach was used to apply results from mechanistic experiments to N₂O flux data resulting from measurements on field scale in southern Germany. Boundary lines were fitted to the rim of the data points in scattergrams depicting readily obtainable soil variables against the measured N₂O flux. The boundary line approach is based on the hypothesis that this line depicts the functional dependency between the two variables. For determining these boundary lines a novel method was applied. The function best representing the relationship between the N₂O flux and soil temperature had a maximum above 23 °C and the one between the N₂O flux and the water filled pore space (WFPS, to represent water content) had a maximum at 72% WFPS. In the range of 0–20 mg N kg^-1 the relationship between N₂O flux and nitrate in the soil was best described by a linear function, whereas in the range of 0–35 mg N kg^-1 a Michaelis–Menten function was more appropriate. The boundary lines specified in this study are in agreement with existing theoretical concepts as well as experimental results obtained under controlled and field conditions as reported in the literature. Therefore, the boundary line approach can be used to improve empirical models for predicting the N₂O flux in the field.     

Further developments in the new approach to boundary condition iteration in optimal control

In solving the boundary value problem resulting from the use of Pontryagin's maximum principle, a transformation matrix is used to relate the sensitivity of the final state to the initial state. This avoids the need to solve the (n × n) differential equation to give the transition matrix, and yields very rapid convergence to the optimum. To ensure convergence, iterative dynamic programming (IDP) is used for a number of passes to yield good starting conditions for this boundary condition iteration procedure. Clipping technique is used to handle constraints on control. Five optimal control problems are used to illustrate and to test the procedure.     

On boundary conditions to the film model of mass transfer in chemical absorption

The problem of appropriate boundary conditions for mass transfer within the liquid film in chemical absorption ih reconsidered. It has been shown that the most general solution to the problem of mass transfer in the liquid film can be obtained if a fixed bulk composition is taken as a film-bulk boundary condition to the differential balance equations of the film. This method leads to solutions which can be incorporated into absorber balance equations of any type. As an illustrative example, the simultaneous absorption of two gases which react together in a semi-batch absorber is discussed. A new, approximate but very simple and accurate solution to this problem is proposed.     

密封环支撑边界条件对机械密封端面变形的影响

机械密封的密封环是通过辅助O形圈支撑在轴上或者密封腔内,不同的结构设计会改变密封环支撑边界。针对三种机械密封结构模型,利用ANSYS有限元分析软件,模拟机械密封摩擦副端面的变形,讨论了橡胶O形密封圈不同受力边界条件下机械密封端面变形的规律。研究发现当动环、静环均采用SiC时,在静态（结构分析）时,该三种不同支撑结构的摩擦副端面均形成发散间隙,端面变形受支撑边界接触应力的影响较大;热结构耦合分析发现其动环、静环端面间隙呈收敛间隙运转时,热边界条件影响更大。当动环采用石墨,静环采用SiC时,发现其端面间隙可能为收敛型也可能为发散型,这与支撑边界有关。故密封环支撑边界条件的不同会影响动环端面变形,同时动、静环材料的弹性模量对端面的变形有较大影响,从而会影响密封性能。该研究对机械密封设计有指导意义。     

A unique approach to predict accurate heavy oil density with new three parameter cubic equation of state

A unique approach is proposed to predict the heavy oil density using a recently developed three parameter cubic equation of state for heavy pure components. It predicts the heavy oil density with an AAD of 2.5%. The new model does not require any experimental density data for its tuning. The basic assumption in this work is that heavy oil is a mixture of n‐alkanes and aromatics as the most prominent groups. Critical pressure characterisation for pseudo fractions is done by tuning a perturbation factor (f_c), also representing the aromaticity, to match the predicted saturation pressure with the experimental pressure. The parameter ‘u’ for the pseudo fractions is adjusted using another parameter ‘S’ which was found to vary linearly with f_c.     

A new analytical model to predict heavy oil production rate in the SAGD process

An analytical model for predicting the oil production rate in the steam-assisted gravity drainage (SAGD) process is presented in this article. The suggested correlation is found based on Butler's original work. It considers the most effective parameters of the process that emphasize the influence of gravity drainage and that are grouped together in the form of the Rayleigh's number. The present model introduces three coefficients (i, j, and k) into the equation, which are determined by minimizing an objective function based on the difference between the six experimental SAGD datasets and the calculated results. The tool chosen for the minimization is the genetic algorithm (GA). After the initial evaluation, the same approach is used for other reservoir characteristics to ensure the robustness of the new equation. Having considered various simulation outcomes with an average error of 8.9% makes this model a credible one for predicting the SAGD production rates. The novelty of the new predictive model lies within its unique approach, making it quite fast and applicable to a wide range of reservoirs with low associated estimation inaccuracies.     

Optimal conditions of isobutane dehydrogenation in radial flow moving bed hydrogen-permselective membrane reactors to enhance isobutene and hydrogen production

In the isobutane dehydrogenation process, coupling reaction and separation and optimization of the intensified process can improve the isobutane conversion and selectivity, reduce operational costs and lets to produce pure hydrogen. In this research, the radial flow moving bed reactors in the Olefex technology have been supported by Pd–Ag membrane plate to remove hydrogen from the reaction zone. The reactions occur in the tube side and the hydrogen is permeated from the reaction zone to the sweep gas stream. The proposed configuration has been modeled heterogeneously based on the mass and energy conservation laws considering reaction networks. To prove the accuracy of the considered model, the simulation results of the conventional process have been compared against available plant data. The Genetic algorithm as an effective method in the global optimization has been considered to optimize the operating condition of membrane reactors to enhance isobutene productivity. In this optimal configuration, the isobutene production has been enhanced about 3.7%.     

An economic model predictive control approach to integrated production management and process operation

Managing production schedules and tracking time‐varying demand of certain products while optimizing process economics are subjects of central importance in industrial applications. We investigate the use of economic model predictive control (EMPC) in tracking a production schedule. Specifically, given that only a small subset of the total process state vector is typically required to track certain scheduled values, we design a novel EMPC scheme, through proper construction of the objective function and constraints, that forces specific process states to meet the production schedule and varies the rest of the process states in a way that optimizes process economic performance. Conditions under which feasibility and closed‐loop stability of a nonlinear process under such an EMPC for schedule management can be guaranteed are developed. The proposed EMPC scheme is demonstrated through a chemical process example in which the product concentration is requested to follow a certain production schedule. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1892–1906, 2017