On the effect of added impurity on crystal purity of urea in an oscillatory baffled crystallizer and a stirred tank crystallizer

Hannah McLachlan, Xiongwei Ni

Research output: Contribution to journalArticle

Abstract

Previous work has indicated that crystals produced in oscillatory baffled crystallisers (OBC) from a relatively ‘pure’ starting environment gave statistically higher purities than that in stirred tank crystallisers (STC) under comparable conditions. In this work, a known amount of biuret (the impurity) was added to the ‘pure’ urea system and the results show that the OBC still produced higher purity crystals than the STC, although these purity values were statistically lower than from the ‘pure’ environment in both vessels. By evaluating crystallisation rates of both urea and biuret, we noticed that these rates are higher in the STC than in the OBC, which would have led to small crystals in the former vessel. The CSD data however gave the opposite result where the CSD is wider with more, large crystals in the STC than in the OBC, in particular in the presence of added impurity. These larger crystals are likely formed due to agglomeration coupled with incorporation of impurity, which leads to a lower purity.
Original languageEnglish
Pages (from-to)81–88
Number of pages8
JournalJournal of Crystal Growth
Volume442
Early online date10 Mar 2016
DOIs
Publication statusPublished - 15 May 2016

Fingerprint

urea
crystal
vessel
agglomeration
crystallization
effect
rate

Cite this

@article{9691ff1a5bc947a48e4daa955c704128,
title = "On the effect of added impurity on crystal purity of urea in an oscillatory baffled crystallizer and a stirred tank crystallizer",
abstract = "Previous work has indicated that crystals produced in oscillatory baffled crystallisers (OBC) from a relatively ‘pure’ starting environment gave statistically higher purities than that in stirred tank crystallisers (STC) under comparable conditions. In this work, a known amount of biuret (the impurity) was added to the ‘pure’ urea system and the results show that the OBC still produced higher purity crystals than the STC, although these purity values were statistically lower than from the ‘pure’ environment in both vessels. By evaluating crystallisation rates of both urea and biuret, we noticed that these rates are higher in the STC than in the OBC, which would have led to small crystals in the former vessel. The CSD data however gave the opposite result where the CSD is wider with more, large crystals in the STC than in the OBC, in particular in the presence of added impurity. These larger crystals are likely formed due to agglomeration coupled with incorporation of impurity, which leads to a lower purity.",
author = "Hannah McLachlan and Xiongwei Ni",
year = "2016",
month = "5",
day = "15",
doi = "10.1016/j.jcrysgro.2016.03.001",
language = "English",
volume = "442",
pages = "81–88",
journal = "Journal of Crystal Growth",
issn = "0022-0248",
publisher = "Elsevier",

}

On the effect of added impurity on crystal purity of urea in an oscillatory baffled crystallizer and a stirred tank crystallizer. / McLachlan, Hannah; Ni, Xiongwei.

In: Journal of Crystal Growth, Vol. 442, 15.05.2016, p. 81–88.

Research output: Contribution to journalArticle

TY - JOUR

T1 - On the effect of added impurity on crystal purity of urea in an oscillatory baffled crystallizer and a stirred tank crystallizer

AU - McLachlan, Hannah

AU - Ni, Xiongwei

PY - 2016/5/15

Y1 - 2016/5/15

N2 - Previous work has indicated that crystals produced in oscillatory baffled crystallisers (OBC) from a relatively ‘pure’ starting environment gave statistically higher purities than that in stirred tank crystallisers (STC) under comparable conditions. In this work, a known amount of biuret (the impurity) was added to the ‘pure’ urea system and the results show that the OBC still produced higher purity crystals than the STC, although these purity values were statistically lower than from the ‘pure’ environment in both vessels. By evaluating crystallisation rates of both urea and biuret, we noticed that these rates are higher in the STC than in the OBC, which would have led to small crystals in the former vessel. The CSD data however gave the opposite result where the CSD is wider with more, large crystals in the STC than in the OBC, in particular in the presence of added impurity. These larger crystals are likely formed due to agglomeration coupled with incorporation of impurity, which leads to a lower purity.

AB - Previous work has indicated that crystals produced in oscillatory baffled crystallisers (OBC) from a relatively ‘pure’ starting environment gave statistically higher purities than that in stirred tank crystallisers (STC) under comparable conditions. In this work, a known amount of biuret (the impurity) was added to the ‘pure’ urea system and the results show that the OBC still produced higher purity crystals than the STC, although these purity values were statistically lower than from the ‘pure’ environment in both vessels. By evaluating crystallisation rates of both urea and biuret, we noticed that these rates are higher in the STC than in the OBC, which would have led to small crystals in the former vessel. The CSD data however gave the opposite result where the CSD is wider with more, large crystals in the STC than in the OBC, in particular in the presence of added impurity. These larger crystals are likely formed due to agglomeration coupled with incorporation of impurity, which leads to a lower purity.

U2 - 10.1016/j.jcrysgro.2016.03.001

DO - 10.1016/j.jcrysgro.2016.03.001

M3 - Article

VL - 442

SP - 81

EP - 88

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

ER -