MCT 1096 a MAX HT SodaliteScaleInhibitor Brochure 3-6-08

8/15/2019 MCT 1096 a MAX HT SodaliteScaleInhibitor Brochure 3-6-08

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MAX HT®

Eliminates Sodalite

Scale Accumulation in

Alumina Refineries



Background

The problem of sodalite scale in Bayer Processalumina production is well recognized anddocumented. When caustic liquor is heated in digesterheaters, dissolved silica reacts with the caustic andalumina to form sodalite, which precipitates as scaleon the hot surfaces of the heater. As scale develops inprocessing equipment, the heating surfaces becomeless thermally conductive, resulting in lower heatingefficiency, or Heat Transfer Coefficient. HeatTransfer Coefficient decays continuously over time

with the accumulation of sodalite scale. This, inturn, reduces evaporation and flow. The end resultfor refineries is loss of caustic and alumina, increased

energy consumption and higher maintenance costs, allof which leads to lower production rates and higherproduction costs.

Up until now, the alumina industry has been forcedto deal with this ever-present problem by removingscale after it has accumulated, which is a costly andtime-consuming proposition.

Cytec’s Answer EmphasizesPrevention over Correction

Cytec’s revolutionary new solution – MAX HT

sodalite scale inhibitor – tackles scale through an

entirely different approach: by preventing it fromforming. MAX HT sodalite scale inhibitor completelyeliminates sodalite scale accumulation in liquor heatexchangers and inter-stage piping. In so doing, itachieves the following:

- enables plants to maintain Heat TransferCoefficient and, thus, efficiency in heat exchangers

- precludes the need to inject steam directlyinto liquor heaters or digesters

- makes acid cleaning of heat exchangersunnecessary

Simply put, MAX HT sodalite scale inhibitorhelps alumina refineries realize increased operatingefficiencies and significant cost savings by renderingthe once ubiquitous problem of sodalite scale into adistant memory. Consider the additional benefits:

- reduce energy consumption- lower costs for sulfuric acid to clean

equipment- eliminate the danger associated with having

plant personnel manually clean equipment- eliminate downtime required for cleaning

MAX HT sodalite scale inhibitor is designed tohelp free refineries from operational constraints, andsolve a problem which the industry currently spendssignificant time, manpower and expenses correcting.

How Does It Work?

Very simply, if solid sodalite is not present in theliquor, then scale cannot form. Our challenge wasto find a product that would prevent solid sodalitefrom forming. The hypothesis that precipitation isreversible if the nuclei do not grow to a critical size

became the foundation of our efforts. MAX HTsodalite scale inhibitor works by having inhibitorsattach to embryos, or “micronuclei,” to stop themfrom growing into “nuclei,” thereby reversing theprecipitation process. This prevents solid particlesfrom ever forming.

Heat Transfer Coefficient

2

Think of thepossibilities...

Soluble IonsEmbryos or

“Micronucler < r*

MAX HT So

Reversible r* Irrever

Heat TransferCoefficientdecay curve of

a normal heatexchanger,without useof MAX HT

sodalite scaleinhibitor.



Benefits to the Customer

MAX HT sodalite scale inhibitor brings a host offar-reaching benefits to alumina refineries.

In the Evaporators:

• Higher Heat Transfer Coefficient promoteshigher levels of evaporation. Depending on theeconomic balance between caustic and energycosts, plants may choose to either:

- run higher mud wash flows, thereby

reducing soda loss (caustic savings) or

- reduce the number of evaporators in service,thus reducing energy consumption

• Improved flashing results in lower live steamdemand for the same evaporation rate, therebyimproving evaporator economy.

• Eliminates acid cleaning/maintenance of sodalitescale accumulation. As a result, there is noneed to change tubes that would otherwise besubjected to acid corrosion.

In the Digesters:

• Increased flashing and evaporation results inthe ability to run higher mud wash water flows,

which reduces soda losses.

• Higher liquor temperature in vapor heatersreduces live steam demand in live steam heaters.

• With cleaner live steam heaters, it is possible toachieve higher liquor-to-digester temperatures.Plants no longer need to reduce liquor flows due

to low digest temperatures. Higher average liquor

flows will therefore be maintained, which resultsin increased production.

• Higher liquor-to-digester temperatures reducesthe need to inject steam directly into thedigesters. This results in:

- Reduction in extraneous dilution –hence, higher mud wash and improvedsoda recovery.

- Reduction in energy consumption –condensate associated with steaminjected into the live steam heater can be

recovered and returned to the powerhouse as boiler feed make-up water(instead of being fed into the digester).The temperature of the make-up water

will now be at ~90˚C, versus ambient~20-30˚C.The chemical treatment required for thisquantity of fresh make-up water is alsoreduced.

• In many plants, as scale accumulates in the livesteam heaters, the steam valves to these heatersopen wider. This results in higher shell side

pressures and, ultimately, higher condensatetemperatures. As the condensate temperaturesincrease, more flashing occurs and significantenergy is lost. MAX HT sodalite scale inhibitoreliminates this.

• High temperature plants that operate a directinjection live steam heater can convert this to anindirect heater, thereby saving energy (condensatereturned to power house) and soda (eliminationof extraneous dilution).

When applied to the

evaporator feed, MAHT sodalite scale

inhibitor has been

proven effective

in the evaporators

and is still beneficia

in the digester

liquor heaters.

Heat TransferCoefficient decurve of a hearun with MAXHT sodalite scainhibitor.

Heat Transfer Coefficient

3

Nucleir = r*

Scale Particlesr > r*

le Inhibitor



Extensive field and

laboratory testing

has revealed no

negative effects on:

predesilication,

digestion, extraction

efficiency, desilication,

mud settling,

hydrate precipitation,

yield, PSD, product

quality, oxalate

precipitation, and

head gases from high

temperature plants.

In addition, the product

causes no interference

with other process

chemicals such as

crystal growth

modifiers and defoamers.

Bauxite Quality/Mining:

• In certain cases, the silica content of bauxiteis critical for the protection of heaters andinter-stage piping. However, with the useof MAX HT sodalite scale inhibitor, thisbecomes less of a concern (assuming productsilica specification is not jeopardized). As aresult, refineries may relax bauxite blendingand mining programs to achieve acceptablesilica levels for proper desilication.

Pre-desilication:

• Pre-desilication to control silica in liquorfor the protection of heaters and pipesfrom scaling may also be severely relaxed(as product quality allows). This couldhave tremendous financial implications forBrownfield and Greenfield expansions.

- The number of tanks required forpre-desilication would be reduced.

- The pumping requirements would besignificantly reduced.

• For existing plants – eliminates dilution fromdirect steam injection, allowing for higher

mud wash and improved soda recovery.• Reduces energy for pumping across the

pre-desilication circuit.

Plant Stability:

A stable alumina plant is highly desirable. Themore stable the operation of the plant, thehigher the rate of production and the greaterthe capacity to optimize processes. Clean heatersand inter-stage piping in both evaporatorsand digesters enhances plant stability throughmaintenance of constant:

• Steam flows (positive impact on thepower co-generating plant)

• Evaporation rates

• Liquor-to-digester flows

• Digest temperatures

• Digester blow-off temperatures(impact on thickener operations)

Extensive Testing Bearsout Product Efficacy

MAX HT sodalite scale inhibitor has undergoneexhaustive pilot and plant testing, which hasdemonstrated the value of the product underactual production conditions. Dosages as low

as 20 ppm have proven effective, though actualdosages depend upon equipment configurationand composition of bauxite.

Product Is Benign to theOverall System

MAX HT sodalite scale inhibitor has beenshown to cause no impact whatsoever on silicaconcentration in digester blow-off. In the presenceof solids, the product will adsorb onto the solids,thereby rendering them innocuous. As MAX HTenters the digesters with the mud solids, it ceasesto be effective. Thus, desilication occurs as pernormal. MAX HT leaves the circuit with the mudand does not build up in the circuit.

In short, MAX HT sodalite scale inhibitor doesonly what it is intended to do – namely, eliminatesodalite scale – and nothing more.

4

www.cytec.com

Although the information and recommendations set forth herein (hereinafter “Information”) are presented in good faith and believed to be correct as of the date hereof, norepresentation as to the completeness or accuracy thereof is made. Information is supplied upon the condition that the persons receiving same will make their own determinationas to its suitability for their purposes prior to use. NO REPRESENTATIONS OR WARRANTIES, EITHER EXPRESS OR IMPLIED, OF MERCHANTABILITY, FITNESS FOR A PARTICULARPURPOSE OR OF ANY OTHER NATURE ARE MADE HEREUNDER WITH RESPECT TO INFORMATION OR THE PRODUCT TO WHICH INFORMATION REFERS.

TRADEMARK NOTICE The ® indicates a Registered Trademarkin the United States and the ™ or * indicates a Trademark in theUnited States. The mark may also be registered, the subject of an

application for registration or a trademark in other countries

• Email: [email protected] Worldwide Contact Info: www.cytec.com US Toll Free: 800-652-6013 Tel: 973-357-3193 •

© 2008 Cytec Industries Inc. All Rights Reserved MCT-1096-A

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MCT 1096 a MAX HT SodaliteScaleInhibitor Brochure 3-6-08

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