Eka® chlorine dioxide
generation systems

We help make pulp
white and bright!
We are Nouryon, a global specialty chemicals leader.
We produce essential chemicals and are experts in highly
demanding chemistry. Nouryon is a specialist in the designand supply of chlorine dioxide plants and equipment to thepulp and chemical industries.
Nouryon has designed, built, re-built, handled spare partsand operated chlorine dioxide (ClO2) systems for pulp
bleaching for over 50 years. As the international leader inClO2 technology, we oﬀer service, support, spare partsand equipment for the large-scale production andapplication of both vacuum and atmospheric processes.
We can supply all the ClO2 processes needed to matchyour requirements, from the design and procurement of
the process equipment to a complete turnkey installation.
Our experience and know-how ranges from rebuilds ofexisting plants to brand new installations. We operate
globally and oﬀer our customers quick and personal
service 365/7.

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Chlorine dioxidesystems
Eka Engineering is a world-leading supplier of chlorine dioxide(ClO2) plants. We have developed a number of diﬀerent
process technologies for safe and eﬃcient ClO2 generation.
The new standard
ClO2 is an oxidizer that has been commercially used
for bleaching pulp since the mid 1940s. Today, ClO2
is a preferred bleaching agent and is used globally inthe majority of pulp mills producing bleached Kraft
pulp.
It is the most cost-eﬀective pulp bleaching agent,achieving high brightness while maintaining high ﬁber
strength. Modern bleaching sequences involving
ClO2 produce a low level of predominantly non-toxic
organo-chlorine (AOX) compounds in the bleach planteﬄuent, making it possible for the pulp mills tocomply with the more stringent AOX discharge
regulations in force in most countries in the world.
These are the main reasons why ClO2, used incombination with oxygen (O2) and hydrogen peroxide(H2O2), has replaced chlorine (Cl2) as a bleaching
agent in most parts of the world. Chlorine dioxide isthe main bleaching agent used in modern

environmentally compatible paper pulp manufacturing.
Chlorine dioxide is the main component in ECF(Elemental Chlorine-Free) bleaching. ECF bleachingis the worldwide bleaching standard and consideredthe "Best Available Technique" for the production of
bleached pulp.
The basic process
ClO2 is produced on site by reducing sodium
chlorate (NaClO3) in an acidic solution, either
under vacuum (SVP processes) or atmospheric(Mathieson, HP-A processes) conditions. Diﬀerent
by-products are produced by varying the type of
reducing agent and acid. The ﬁrst commercially
viable process for producing ClO2 used sulfur
dioxide (SO2) as a reducing agent - i.e. theMathieson process.
Since then, several new processes have beendeveloped, providing improved ClO2 yield, diﬀerent
by-products and minimized environmental impact.

The SVPprocesses
The SVP (single vessel process) chlorine dioxide process family
consists of a number of similar processes based on the sameequipment conﬁguration. It is relatively easy to switch from one
to the other.
The diﬀerent processes are distinguished from eachother by use of diﬀerent reducing agents and acids
for converting sodium chlorate (NaClO3), to chlorine
dioxide (ClO2). The most common process today isthe SVP-LITE process based on the use of methanol(CH3OH).
SVP-LITE Process
The production of ClO2 in the SVP-LITE process isbased on the reaction between NaClO3, sulfuric acid
(H2SO4), and CH3OH. The heart of the process is an
all-titanium ClO2 generator, a large vessel in which
the NaClO3 is reacted to form ClO2.

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The generator is designed to optimize reaction
eﬃciency, promote salt crystal growth, provide
eﬃcient liquid-gas separation and provide suﬃcientvolume for easy control of reactant concentrations.
A titanium pump circulates the generator solution
through the reboiler. Unique to the process is thatthe components in the circulation loop are
carefully designed to minimize the boil-outs. Thewater evaporation rate matches the rate at which
the water enters the generator with the chemicalfeeds and utilities. The ClO2 partial pressure ismaintained at a safe level by means of a strong
vacuum and dilution with water vapor.

SVP-SCW Process

Nº 2 Filter
Ejector

H.P.
Steam

Vent Fan

SystemEjector

Quench Water
Tank
Nº 2 Saltcake
FilterNº 1 Saltcake
FilterNº 1 Filter
ReceiverNº 2 Filter
Receiver

MiscVents

Nº 1 Filter
Ejector

DelugeQuenchSystemCondenser
Spray
QuenchDissolving
Tank

Generator
Condenser

Metathesis
Pump

SaltcakeSol. Pump

Metathesis
Tank

Vent
Scrubber

Scrubber
Pump

ChilledWater

To Bleach
Plant
AcidFeed
Reboiler
Generator

Steam

Condensate
Tank

Condensate
Pump

MeOH/
NaClO3Feed

Absorber

AbsorberPump

ClO2
Storage

Generator
Circ. Pump
Saltcake
Filter Pump

Gas absorption

SVP-SCW – Salt Cake Wash System

The chlorine dioxide (ClO2) gas leaving the generator
is cooled in the generator condenser and absorbed
in a packed tower, the ClO2 absorber, by means ofchilled water. The resulting product is a strong solutionof ClO2 with negligible levels of chlorine gas (Cl2).

The SVP-SCW process is an add-on option to theSVP-LITE process. The formed salt cake in SVP-LITE issodium sesquisulfate (Na3 H(SO4 )2 ), which is an acidic
version of sodium sulfate (Na2SO4), containing about
18 wt% of sulfuric acid (H2SO4).

The solution is then pumped to storage tanks for further
use in the bleaching process. As the gas from the ClO2
generator does not contain any diluting gases like air orchlorine, absorption eﬃciency is high and ClO 2concentrations in excess of 10 g/l can easily be reached.

In the SVP-SCW process, the ﬁltered Na3H(SO4)2 crystals
are transferred to a metathesis tank. Here the Na3H(SO4)2 isseparated into its Na 2 SO 4 and H 2 SO 4 components.
The metathesis tank slurry is pumped to a second salt
cake ﬁlter where the neutral Na2SO4 crystals are removed
and sent to the mill’s recovery system. The ﬁltrate fromthe second ﬁlter, containing the H2SO4 to be recovered,is discharged back to the SVP generator.

Typically, the vacuum in the ClO2 generation system iscreated by means of a steam ejector, but a liquid ringvacuum pump could also be used.
After passing the ejector, the tail and vent gases are washedwith chilled water in the vent scrubber. The eﬄuent waterfrom the scrubber is transferred to the main absorption
tower and thus all the ClO2 in the vent gases is recovered
and added to the produced ClO2 solution.

Other SVP processes
SVP-HP
The SVP-HP process is based on use of hydrogen peroxide(H2O2) for reduction of sodium chlorate (NaClO 3) in anacidic sulfuric acid (H2SO4) solution to form ClO2. Byproducts are Na2SO4 or Na3H(SO4)2 and oxygen (O2).

Sodium sulfate recovery

SVP Standard

The sodium sesquisulfate crystals (Na3H(SO4)2) formedin the generator are pumped to a titanium bottom feed,rotary drum ﬁlter for removal as a near dry solid. Theﬁlter is equipped with a hot water wash system. Thewash water and generator liquor are withdrawn from theﬁlter and returned to the generator, leaving behind adry, high-quality salt cake. The Na3H(SO4)2 is dischargedinto the dissolving system and pumped to the pulp mill.

NaClO3 is reacted with sodium chloride (NaCl) in a H2SO4
solution to form ClO2 and Cl2. The salt cake by-productconsists of neutral Na2SO4.

This ﬁlter comes standard with a tantalum ﬁlter cloth,providing years of trouble-free service and high reliability.
The ﬁlter is much less sensitive to crystal size or
production rate ﬂuctuations than competing top feedﬁlters.

SVP Partial HCI
In this process, NaClO 3 is reacted with NaCl andhydrochloric acid (HCl) in a H2SO4 solution to form ClO2
and Cl2. This will give a substantial reduction in by-product
Na2SO4 compared to SVP Standard.
SVP Total HCI
NaClO3 is reacted with HCl, which acts as both a reducing
agent and an acid. NaCl is produced as a by-product.

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HP-A ClO2
processThe HP-A is one of the newest processes introduced by Nouryon.
This proprietary technology has several advantages
over earlier atmospheric chlorine dioxide (CIO2) processes.
HP-A chemistry
Sodium chlorate (NaCIO3) reacts in a two-stage
reactor system with a proprietary grade of hydrogenperoxide (H2 O2 ) in sulfuric acid (H2 SO4 ) solution toproduce CIO2. The reaction by-products are oxygen(O2) and spent acid containing sodium bisulfate(NaHSO4).

The HP-A process oﬀers the customer the opportunity
to expand ClO2 production capacity with the existing
generator. The older atmospheric ClO2 processes use
other reducing agents. Some of the reducing agents
contain sodium chloride (NaCl) and then form chlorinegas (Cl2) as a by-product. Sulfur dioxide (SO2) andmethanol (CH3OH) are also used as reducing agents.

You normally need the following systems in association with thechlorine dioxide (CIO2) equipment:
Chlorate, acid and reducing agent storage and delivery
ClO2 product storage and delivery
Chilled water supply
Our extensive experience in this ﬁeld has enabled us to become experts in thedesign and installation of customized systems.

6World-class service and spareparts. We oﬀer the following
service and support:
Optimization• Assessment of chemical yield on sodium chlorate,reducing agent and acid
• Chlorine dioxide production capacity tests• Saltcake removal & utilization• Vent system emissions recovery• Investigations of emissions to both air and sewers• Advanced process control implementation
Operational Support• Advanced process control consultation• Remote or on-site troubleshooting• Applied Kepner-Tregoe methods• Root cause analysis• Maintenance planning assistance• 24 - 7 availability• Inspection and advice on sodium chlorate, sulfuric
acid, methanol, hydrogen peroxide and chlorine
dioxide storage• Investigations of process and production limitationsin the chlorine dioxide plant
Process safety• Participation in safety audits and risk analysis at thechlorine dioxide plant• Interlock checkouts for Process Safety Management(PSM) program• Process Hazard Analysis (PHA) re-validation formethanol, chlorine dioxide, turpentine, ammonia
and non-condensable gas (NCG) systems• Supporting documentation / process safety
information / Management of Change (MOC)
process veriﬁcation• PHA Facilitation & OEM Process ExpertTraining• Operator training• Safety training• Laboratory analysis
Spare parts• Our spare parts service will help ensure your plant
availability is maximized and any downtime is minimized.
• We deliver all parts rapidly and reliably using ourextensive supply chain and global logistics network.
• For quality assurance, we deliver spare parts fromthe original supplier whenever possible. Some typicalspare parts we provide include pump parts, instruments,valves, and ﬁlter inserts.

7Nouryon Sales Oﬃces

EuropeGothenburg, Sweden
T +46 31 587000

South AmericaJundiaí, São PauloT +55 11 4589 4800

Asia
Shanghai, China
T +86 21 2289 1000

E-mailbleaching_experts@nouryon.com

About Nouryon
Nouryon is a global, specialty chemicals leader. Markets andconsumers worldwide rely on our essential solutions tomanufacture everyday products, such as personal care, cleaning
goods, paints and coatings, agriculture and food,pharmaceuticals, and building products. Furthermore, thededication of more than 7,900 employees with a sharedcommitment to our customers, business growth, safety,
sustainability and innovation has resulted in a consistently strong
financial performance. We operate in over 80 countries aroundthe world with a portfolio of industry-leading brands. Visit ourwebsite and follow us Nouryon and on LinkedIn.

Learn more about
Nouryon’s Eka Technologies
eka.nouryon.com

Eka®, SVP®, SVP-LITE® and HP-A® are registered trademarks of Nouryon in several countries worldwide.