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A new method of potassium chromate production from chromite and KOH‐KNO 3 ‐H 2 O binary submolten salt system
Author(s) -
Sun Zhi,
Zhang Yi,
Zheng ShiLi,
Zhang Yang
Publication year - 2009
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.11871
Subject(s) - chromite , chemistry , chromate conversion coating , potassium chromate , decomposition , chromium , potassium hydroxide , inorganic chemistry , salt (chemistry) , potassium , oxygen , potassium nitrate , organic chemistry
A new method of chromate production by applying a new reaction system of KOH‐KNO 3 ‐H 2 O (binary submolten salt system) is proposed and proved feasible. Under conditions of temperature 350°C, KOH‐to‐chromite ore ratio 2:1, stirring speed 700 rpm, KNO 3 ‐to‐chromite ore ratio 0.8:1, oxygen partial pressure 50%, and gas flow 1 L/min, chromium conversion ratio obtained is >98% with reaction time around 300 min. The decomposition of chromite ore in the system is a typical process of solid– liquid–gas reaction, which is coordinately controlled by mass diffusion in product layer and interface reaction. Apparent activation energy of decomposition in the temperature range from 280 to 370°C is 55.63 kJ/mol. During reaction, oxygen dissolves into KOH‐KNO 3 ‐H 2 O melt system first and some cluster, e.g. O 2 2− , is formed and the mass diffusion coefficient of the cluster was calculated. The system can be considered as both a media of oxygen transportation and reactant donator. Potassium nitrate plays a role of catalyst in the oxidation decomposition reaction of chromite ore and potassium hydroxide. © 2009 American Institute of Chemical Engineers AIChE J, 2009