Particle size distribution of gypsum crystals in four continuous flow stirred slurry reactors in series

Date

2005-11-07

Author

ÇAKAL, GAYE ÖZGÜR
Özkar, Saim
Eroǧlu, I.

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

87
views

0
downloads

Colemanite (2CaO·3B2O3·5H 2O), one of the important boron mineral, is dissolved in aqueous sulfuric acid to produce boric acid. In this reaction, gypsum (CaSO 42H2O) is obtained as a by-product. Gypsum crystals are in the shape of thin needles. These crystals should be grown to an easily filterable size in order to increase the production yield and purity of boric acid. In this paper, the shapes and the volume weighted mean diameters of the gypsum crystals obtained in the four continuous flow stirred slurry reactors in series were compared. During the experiments, the temperature of the reactors was kept constant at 85°C, and complete mixing was attained at the stirring rates of 400 rpm. The ratio of molar feed rates of colemanite to sulfuric acid, were kept constant either at 1.00 or 1.37. The colemanite feed rate was varied in the range of 5-15 g/min. In all the experiments, colemanite mineral, having particle size smaller than 250 μm, was used. The operating parameters were liquid residence time (17 min, 23 min and 35 min) and volume fraction of solid in the reactors (0.04 and 0.06). Solid samples were collected from each of the four continuous reactors after the reactors had reached to steady state. The reaction between colemanite and sulfuric acid was almost completed in the first reactor, however the gypsum crystal growth continued in the other reactors as well as first reactor. The maximum mean diameter of crystals was found either in the first or second reactor, whereas in the latter reactors due to breakage their mean diameters decreased. The comparison of the images showed that as the residence time increased, the crystals grew bigger. The increase of the solid hold-up from 0.04 to 0.06 at the same residence time (17 min) had also a pronounced effect on the mean diameters of the gypsum crystals.

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=27344433441&origin=inward
https://hdl.handle.net/11511/102641

Journal

VDI Berichte

Collections

Graduate School of Natural and Applied Sciences, Article

Suggestions

OpenMETU
Core

Dynamic Behavior of continuous flow stirred slurry reactors in boric acid production Yücel Çakal, Gaye Ö; Eroğlu, İnci; Department of Chemical Engineering (2004) One of the most important boron minerals, colemanite is reacted with sulfuric acid to produce boric acid. During this reaction, gypsum (calcium sulfate dihydrate) is formed as a byproduct. In this study, the boric acid production was handled both in a batch and four continuously stirred slurry reactors (4-CFSSR̕s) in series system. In this reaction system there are at least three phases, one liquid and two solid phases (colemanite and gypsum). In a batch reactor all the phases have the same operating time (...
Gypsum crystal size distribution in four continuous flow stirred slurry boric acid reactors in series compared with the batch Cakal, GO; Eroglu, I; Özkar, Saim (Elsevier BV, 2006-04-15) Colemanite, one of the important boron minerals, is dissolved in aqueous sulfuric acid to produce boric acid. In this reaction, gypsum is obtained as a by-product. Gypsum crystals are in the shape of thin needles. These crystals should be grown to an easily filterable size in order to increase the production yield and purity of boric acid. In this paper, the particle size distributions and the volume-weighted mean diameters of the gypsum crystals obtained in batch and continuous flow systems were compared. ...
Surface Modification and Characterization of Multi-Walled Carbon Nanotube Kanbur, Yasin; Kucukyavuz, Zuhal (Informa UK Limited, 2011-01-01) Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized by using sulfuric acid and nitric acid. The functionalization was done with two different acid ratio. The functionalized nanotubes were characterized with Fourier Transform Infrared Spectroscopy, X-Ray Photon Spectroscopy, Thermal Gravimetric Analysis, Elemental Analysis, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy. Sulfonation of carbon nanotubes (CN) increased the electrical conductivity of carbon nanotubes ...
Chemical synthesis of pure and Gd-doped CaZrO3 powders Gonenli, IE; Tas, AC (1999-01-01) Aqueous solutions of calcium chloride (CaCl2.2H(2)O) and zirconium oxychloride (ZrOCl2.8H(2)O), in appropriate volumetric amounts, were used as the starting chemicals in the synthesis of phase-pure CaZrO3 powders. Rare earth element dopings (up to 25 at%) were performed by using the aqueous chloride solutions of gadolinium (Gd). Formation of CaZrO3 powders were achieved by two different chemical synthesis techniques: (i) self-propagating combustion synthesis, and (ii) precipitation in the presence of EDTA b...
Kinetics of gypsum formation and growth during the dissolution of colemanite in sulfuric acid Cetin, E; Eroglu, I; Özkar, Saim (2001-11-01) One of the most important boron minerals, colemanite, is dissolved in aqueous sulfuric acid to produce boric acid whereby gypsum is formed as byproduct. Filtration of gypsum has an important role in boric acid production because gypsum affects the efficiency, purity and crystallization of boric acid. The formation and growth kinetics of gypsum during the dissolution of colemanite in aqueous sulfuric acid were studied in a batch reactor by varying the temperature (60-90 degreesC), stirring rate (150-400 rpm)...

Citation Formats

G. Ö. ÇAKAL, S. Özkar, and I. Eroǧlu, “Particle size distribution of gypsum crystals in four continuous flow stirred slurry reactors in series,” VDI Berichte, no. 1901 I, pp. 465–470, 2005, Accessed: 00, 2023. [Online]. Available: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=27344433441&origin=inward.