AkzoNobel SodiumChlorate Process Detail Tcm56-90538
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© AkzoNobel Pulp and Performance Chemicals Sodium Chlorate Process Red stream • The sl urry i s dewatered using a sc rew thickener, washed, filter ed and dr ied. • The chlorate product is then packed and ready f or deli very to cus tomers. Light blue stream • Wat er vapor exi ting t he vacuum cry stalli zer Yellow stream • An electrolyte side st ream from the ci rcul ation l oop is alkal ized by addit ion of NaOH, filter ed to remove precipitations that resulted from the alkalization, and fed to a crystallizer . Green stream • Incoming salt is dissol ved and then purified to r emove impurities (e.g., calcium and magnesium) that could harm the electrolysis operation by precipitating on the electrodes, resulting in higher electrode potentials. • The evapor ator r ecr ystal lizes t he sal t t o r emove sulfate ions, which can otherwise harm the anode operation, resulting in increased levels of byproduct oxygen. Careful environmental control of all outlet streams is necessary, in particular as the process contains chromium (VI) and chlorate which can be harmful to living organisms. Orange stream The purified salt is dissolved into chlorate electrolyte and enters the electrolyte circulation, which runs through several steps: • Cool ing is necessary because excess heat is generated from irreversible losses in the electrochemic al cells - about 50% of the electrical energy added ends up as heat that can be used in the process for evaporation steps and/or for external district heating. • Hy dr ochl or ic ac id is added to the elect rolyte prior to the electrolysis, because active chlorine escaping with the cell gas, lowering the pH of the electrolyte • The electr oly te enters the electr oly sis cel ls – chloride ions are oxidized on the anodes and water is reduced on the cathodes, producing hydrogen gas. • Gas fr om t he elect rolysi s cells and reactor tanks is purified by scrubbing with alkaline to remove chlorine. Additional gas purification methods may be necessary, depending of the specific use of the hydrogen product. • A sodium chl or ate cr ys tal sl ur ry exi ts t he vacuum crystallizer
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Transcript of AkzoNobel SodiumChlorate Process Detail Tcm56-90538
7/24/2019 AkzoNobel SodiumChlorate Process Detail Tcm56-90538
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© AkzoNobel Pulp and Performance Chemicals
Sodium Chlorate Process
Red stream
• The slurry is dewatered using a screw thickener, washed, filtered and dried.
• The chlorate product is then packed and ready for delivery to customers.
Light blue stream• Water vapor exiting the vacuum crystallizer
Yellow stream
• An electrolyte side stream from the circulation loop is alkalized by addition of NaOH, filteredto remove precipitations that resulted from the alkalization, and fed to a crystallizer.
Green stream
• Incoming salt is dissolved and then purified to remove
impurities (e.g., calcium and magnesium) that could
harm the electrolysis operation by precipitating on theelectrodes, resulting in higher electrode potentials.
• The evaporator recrystallizes the salt to remove
sulfate ions, which can otherwise harm the anode
operation, resulting in increased levels of byproduct
oxygen.
Careful environmental control of all outlet streams is necessary, in particular as the process contains chromium (VI) and chlorate which can be harmful to living
organisms.
Orange stream
The purified salt is dissolved into chlorate
electrolyte and enters the electrolyte circulation,
which runs through several steps:
• Cooling is necessary because excess heat
is generated from irreversible losses in the
electrochemical cells - about 50% of the
electrical energy added ends up as heat that
can be used in the process for evaporation
steps and/or for external district heating.• Hydrochloric acid is added to the electrolyte
prior to the electrolysis, because active
chlorine escaping with the cell gas, lowering
the pH of the electrolyte
• The electrolyte enters the electrolysis cells –
chloride ions are oxidized on the anodesand water is reduced on the cathodes,
producing hydrogen gas.• Gas from the electrolysis cells and reactor
tanks is purified by scrubbing with alkaline to
remove chlorine. Additional gas purification
methods may be necessary, depending ofthe specific use of the hydrogen product.
• A sodium chlorate crystal slurry exits the
vacuum crystallizer
