Mathematical modeling and design of layer crystallization in a concentric annulus with and without recirculation

A solution layer crystallization process in a concentric annulus is presented that removes the need for filtration. A dynamic model for layer crystallization with and without a recirculation loop is developed in the form of coupled partial differential equations describing the effects of mass transfer, heat transfer, and crystallization kinetics. The model predicts the variation of the temperature, concentration, and dynamic crystal thickness along the pipe length, and the concentration and temperature along the pipe radius. The model predictions are shown to closely track experimental data that were not used in the model's construction, and also compared to an analytical solution that can be used for quickly obtaining rough estimates when there is no recirculation loop. The model can be used to optimize product yield and crystal layer thickness uniformity, with constraints on the supersaturation to avoid bulk nucleation by adjusting cooling temperatures in the core and jacket. © 2013 American Institute of Chemical Engineers

Mathematical modeling and design of layer crystallization in a concentric annulus with and without recirculation [Abstract]

Mathematical modeling and design of layer crystallization in a concentric annulus with and without recirculation [Abstract

Data_Sheet_1_Epidemiological characteristics of occupational chemical poisonings in Zhejiang, China from 2006 to 2020: A descriptive analysis.PDF

ObjectiveAs the second most common occupational disease in China, occupational poisoning is one of the major public health problems that seriously affect workers' health. This study aimed to investigate the epidemiological and occupational characteristics of acute and chronic occupational poisoning cases in Zhejiang Province, so as to provide a scientific basis for proposing intervention measures and preventive strategies of occupational poisoning.MethodsThe data on occupational poisoning cases in Zhejiang Province from 2006 to 2020 was derived from the National Occupational Disease Network Direct Report System. A descriptive statistical analysis was employed on this data utilizing R software.ResultsFrom 2006 to 2020, 1,008 occupational poisoning cases were reported in Zhejiang Province, with a downward trend since 2007. Of these cases, 81.94% were chronic poisoning and 18.06% were acute poisoning. Ningbo reported the most occupational poisoning cases among the 11 cities in Zhejiang Province, accounting for 20.34% of the total cases. Besides, the occupational poisoning cases in Wenzhou, Jiaxing, and Shaoxing also accounted for 18.15%, 18.06%, and 17.76% of the total number of cases, respectively. Occupational poisoning in male were 693 cases and in female 315 cases. Most of the occupational poisoning cases studied involved people aged between 40 and 49 years (38.19%). The length of work in chronic occupational poisoning cases was significantly higher than that of acute occupational poisoning cases (P ConclusionAlthough the cases of occupational poisoning in Zhejiang Province have declined, more comprehensive and effective prevention and control measures are still needed. More attention ought to be paid to the management of key points according to the epidemiological and occupational characteristics of occupational poisoning cases.</p

Modification of Crystal Shape through Deep Temperature Cycling

The evolution of particle shape is an important consideration in many industrial crystallizations. This article describes the design of temperature-cycling experiments (between alternating positive and negative supersaturations) to substantially change crystal shape with only a small number of cycles. The growth and dissolution of monosodium glutamate crystals of varying shapes were monitored using in-process attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), focused beam reflectance measurement (FBRM), particle vision and measurement (PVM), and off-line optical microscopy. The growth and dissolution kinetics were estimated in a multidimensional population balance model based on solute concentration and crystal dimension measurements. This model fitted the experimental data with a limited number of parameters of small uncertainty. In addition, with the estimated kinetic parameters, the model predicted the crystal size and shape distribution in a different temperature-cycling experiment reasonably well. In contrast to previous studies that have estimated kinetics along multiple crystal axes in mixed-tank crystallizers, this study implements dissolution terms in the multidimensional population balance model along multiple axes