Spray drying conditions and encapsulating composition effects on formation and properties of sodium diclofenac microparticles

This paper reports the preparation and characterization of sustained release sodium diclofenac microparticles by spray drying. Aqueous dispersions of ethyl cellulose (Surelease®) and Eudragit RS 30 D® were evaluated as controlled release polymers. The product properties (product moisture, size distribution, particle morphology, flow properties, total drug load, in-vitro dissolution studies, and encapsulating efficiency) were determined as a function of inlet temperature of the spray drying, the feed flow rate and composition of the microencapsulating formulation. In general, lower values of the product moisture content were observed at higher drying temperatures. The spray-dried product was composed mainly by rounded-shape and multi-size particles. The mean particle diameters of the Eudragit based microparticles tended to be slight bigger than the Surelease based microparticles. The spray dried microparticles showed delayed drug dissolution rates, sustaining the drug release for several hours. These findings confirm the feasibility of the spray drying for preparation of microparticles with sustained release properties. The physical and chemical properties of the microparticles can be changed by varying the spray drying parameters as well as the microencapsulating formulation.     

PVC发泡制品用助剂--优泡剂

分析了PVC发泡制品成型加工时存在的缺陷,说明了添加优泡剂可弥补PVC发泡制品的缺陷,提高泡孔质量,介绍了优泡剂的品种和使用场合及使用量。     

NMR imaging and differential scanning calorimetry study on drying of pine,birch, and reed pulps and their mixtures

Drying, water fractions, and water distribution were investigated for pine, birch, and reed pulps and pine–birch, pine–reed, and pine–birch–reed pulp mixtures. Gravimetrically determined drying times showed that the drying rates of the pulps decreased at two to four inflection points. Characterizations of the dried pulps by differential scanning calorimetry (DSC) showed a faster removal of free water than freezing and nonfreezing bound waters; all decreased simultaneously, however. DSC also revealed the critical water contents at which the free water and freezing bound water disappeared. The gravimetrically determined inflection points of the drying curves corresponded with the critical points determined by DSC. NMR line widths and images produced by ¹H‐NMR imaging revealed the nature and regions of the pulp drying. The constant growth rate of the NMR line widths with decreasing water content appeared to change at two inflection points, which fell approximately in the same water content regions as the inflection points of the drying curves. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 937–945, 2006     

脱硫吸附剂与吸附脱硫技术

综述了国内外原料气和燃料油吸附脱硫技术在吸附脱硫材料和吸附脱硫工艺方面的研究与开发进展。介绍了分子筛类、金属氧化物类、活性炭类等脱硫吸附剂。分别评述了物理吸附、活化吸附、选择性吸附等燃料油吸附脱硫技术的机理和工艺。     

DEVELOPMENT AND VALIDATION OF A PROCESS SIMULATOR FOR DRYING SUBBITUMINOUS COAL

Drying subbituminous coal has never been practiced commercially. The commercial dryers built to date have been designed for drying surface moisture in conjunction with upstream coal preparation facilities. This type of drying is mainly controlled by input energy and the basis of the design is an energy balance. In drying inherent moisture from subbituminous coal, the thermal conductivity of the coal and the diffusion of molecular water within coal particles impose limitations on the process conditions. Energy input and solids residence time in the dryer have to be controlled properly for simultaneously balancing the heat and mass transfer within the coal particles. Improper control of either parameter can cause fires and explosions during the key steps of the drying process—drying and cooling

In parallel to the Anaconda coal drying pilot plant program, a cross-flow, fluid-bed coal drying/cooling process simulator was developed for: (1) understanding the drying phenomena on an individual particle basis; (2) analyzing potential risks and safety limits, and (3) designing the Anaconda pilot plant program

The development of the process simulator was based on both first principles and laboratory data and can be divided into two phases:

1 Development of a semi-mechanistic drying model for Powder River Basin subbituminous coal employing an analytical solution of the diffusion equation

2.Formulation of a fluid-bed cross-bed cross-flow dryer/cooler simulator employing simultaneous heat and mass transfer

This model was validated against process variables data taken on a 4 tph pilot plant. An operable range, or process envelope, has been developed through the pilot plant experience and the process simulation study. Based on the model predictions, an uncertainly range was defined in the design recommendations of a pioneer coal drying plant in scale-up.     

Dehulling of canola by hydrothermal treatments

Hydrothermal pretreatments for loosening the hull of Westar canola (Brassica napus L.) to promote dehulling of the seeds were investigated. The samples tested had on average 14.5% hull on a mass basis. Conditioning treatments involved soaking the seeds in distilled water or exposing the seeds to saturated steam. The moistened seed was treated with one of the following drying methods: unheated-air drying, infrared drying, and fluidized-bed drying. The dried grain was milled in an abrasive dehuller to break the hulls loose. The hulls were removed from the mix by aspiration. The treated seeds yielded a minimum of 11.4% to a maximum of 14.9% of the seed mass as the hull fraction. Nontreated seeds yielded 9.4% of the seed mass in hull fraction after abrasive dehulling and aspiration. Among treatments, raising the moisture content of the whole seed from 6 to 15% by exposure to steam, followed by drying in a fluidized bed, resulted in the maximum percent dehulling efficiency. The hull fraction contained about 24% crude fiber, 18% oil, and 18% protein on a dry-mass basis.     

An Investigation of Error Sources in Computational Fluid Dynamics Modelling of a Co-current Spray Dryer

The paper is focused on identifying error sources in computational fluid dynamics(CFD) predictions of a spray drying process. Seven groups of drying and atomisation parameters were selected for analysis and 13 simulation trials were performed. The theoretical results were compared with experimental data and sensitivity of the simulation results to the analysed factors was determined. The following parameters affecting the accuracy of CFD spray modelling were found: gas turbulence model, particle dispersion, atomising air, initial parameters of atomisation and heat losses to the environment. A major difference in the errors committed during modelling of spray drying process for fine and coarse sprays was observed.     

干燥过程模型化

为了更好地了解和分析各类干燥过程，优化设计，操作和控制，干燥过程数学模型与模拟优化已成为主要研究方向。本文扼要介绍干燥过程数学模型化方法与内容，举例列出了气流干燥过程六为量常微分方程组。