Critical seed loading from nucleation kinetics

A method is presented for preparing critical seed loading diagrams for nonaggregating systems knowing only the nucleation kinetics. This is advantageous because it is much less time‐consuming than developing and solving a complete batch process model including solubility expressions and growth rate kinetics. Furthermore, there are many more reports available in the literature of nucleation kinetics alone than there are of complete batch crystallization process models, because expressions for the nucleation rate as a function of crystal growth rate can be rapidly determined from mixed‐suspension, mixed‐product‐removal (MSMPR) data without measuring the supersaturation. The results for 43 systems show that there is a great deal of variability in the critical seed loading, and a single correlation is inadequate to describe the relationship between critical seed loading and seed size. For a seed size of 10 µ, seed loading can effectively suppress nucleation in 92% of cases, while for seeds of size 50, 100, and 200 µ, seed loading can suppress nucleation in 74, 61, and 39% of cases, respectively. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1645–1653, 2014     

生物技术在屠宰废水处理中的应用研究进展

屠宰废水富含油,碳氮比、碳磷比高,且水质变化较大,是一类典型的有机废水。系统地介绍了目前国内外屠宰废水的主要生物处理技术及其研究现状,结果表明:单一的生物处理技术降解此类废水,很难达到预期效果,SBR组合工艺将是处理屠宰废水经济有效的工艺。     

Integrated production scheduling and batch delivery with fixed departure times and inventory holding costs

In this paper, we address a model for supply chain coordination. There are m manufacturers modelled as single machines, each of which processes a specific set of jobs (products). After processing is completed, jobs are batched, and batches are shipped to a customer by means of vehicles. The problem consists in concurrently finding a production schedule of the jobs, a partition of jobs into delivery batches and an assignment of delivery batches to vehicles, so that jobs are delivered within their deadlines and total costs are minimised. We focus on a scenario characterised by fixed departure times and inventory holding costs. For each departure time there is a given number of vehicles, possibly having limited capacity. Each job incurs a cost proportional to the time from job completion to delivery departure. In this paper, we show that the problem is NP-hard even for a very restricted case, and report various polynomiality results for two scenarios, namely: (i) when the production sequence of each manufacturer is fixed in advance, and (ii) when there is a single manufacturer and processing times are all equal to 1. We also point out several open problems.     

Biodegradation kinetics of a mixture of phenols in a sequencing batch moving bed biofilm reactor under starvation and shock loads

BACKGROUND: The objective of this research was to study the biodegradation kinetics of a mixture of phenol, 4‐chorophenol 2,4‐dichlorophenol and 2,4,6‐trichlorophenol in a moving bed sequencing batch reactor (SBR) subjected to starvation and shock loads. The effect was evaluated on the degradation time and on the specific degradation rate. RESULTS: The bacteria present in the system degraded effectively the mixture of phenols. Degradation efficiencies were higher than 98% as total phenols and greater than 95% as organic carbon. It was observed that starvation and shock loads had only a transient effect on microorganisms degradation rate. The substrate removal rate decreased when the perturbations were applied, but for subsequent SBR cycles the previous activity was recovered. Results also demonstrated that suspended biomass was more sensitive to changes than the attached biomass present in the moving bed. CONCLUSIONS: The moving bed SBR presented robust performance under variable influent concentrations of a mixture of inhibitory compounds. Copyright © 2011 Society of Chemical Industry     

Average dwell time-based optimal iterative learning control for multi-phase batch processes

Multi-phase batch process plays an important role in modern industry, especially for processes with different dimensional phases. As the different phases may interact with each others deeply, when and how to perform the transfer between adjacent phases highly affect the control performance and product quality. Meanwhile, the running time in different phases influence the production efficiency. Therefore it is of crucial importance to study the control of multi-phase batch processes with time constraints. Take the injection molding process as an example, a multi-phase batch process can be regarded as a switched system with different-dimensional subsystems in each batch. In this paper, the multi-phase batch process is converted to an equivalent two-dimensional (2D) switched system and the repetitive and 2D nature of batch processes is explored. Within the framework of 2D system theory, both the exponential stability and the shortest running time are considered. Meanwhile, a compound 2D controller with optimal performance is designed. The contributions of this paper are as follows: (1) the batch process studied is with different dimensions in each phase. (2) using the average dwell time method, a sufficient condition ensuring the exponential stability is obtained, meanwhile, the minimum running time of each subsystem, i.e., the running time of each phase can be calculated. Finally, the proposed method is illustrated with an injection molding process to show the effectiveness.     

Excel在玻纤配合料计算中的应用

介绍了在玻璃纤维生产中,利用Excel中的规划求解工具进行玻纤配合料的计算步骤,以实例详细阐述了玻纤配合料的计算过程,说明如何保存和使用一个非常简单实用的Excel计算模型,从而提高生产过程中工程技术人员的工作效率和计算精度。经过验证,计算结果准确无误。