Question: What is the total water consumption including hydrolysis water additions and steam injection in kg water per kg IPA produced?

ISOPROPYL ALCOHOL

THE PROCESS FLOW DIAGRAM IPA

IUPAC

ECONOMIC

PRODUCTION

ISOPROPYL
ALCOHOL

HEALTH
AND SAFETY

CHEMICAL
PROPERTIES

PHYSICAL

USES

PROPERTIES

PHYSICAL PROPERTIES

ODOUR

-STRONG

SOLUBILITY

ALCOHOL

COLOUR

-SOLUBLE IN

ALL ORGANIC

-COLOURLESS

-INSOLUBLE IN

SALT

MOLAR MASS

Physical
properties

BOILING

-60.09

POINT

mol 1

g

82.5°C

Fairly

MICSIBLE

volatile

evaporates
easily

IN WATER

MELTING

POINT

-89°C

Dehydrogenation

Oxidation

Etherification

•Halogenations

CHEMICAL PROPERTIES

PRODUCTION METHOD

* Direct

Indirect

SOUTHWAY

SOUTH

AM

USES

* pharmaceutical industry

× Construction field -wood

* Plantation industry -pesticides

* Cosmetics -baby oils, lotions, etc.
* Aerosol -hair spray, detergents, etc.
* Removing sticky residue

HEALTH AND SAFETY

*Industry (not harm)

*Highly

flammable/explode-away

from heat, open flame, ignition

sources and incompatibles

*Defect to human skin -use glove

ECONOMICS

*rose by 5% to $1240/tonne from
$1200/tonne in mid-April

*Geo Chem Trading located in
Penang Port, Butterworth Penang.

BLOCK DIAGRAM
FOR INDIRECT

HYDRATION OF

I SOPROPYL

ALCOHOL

INPUT (RAW MATERIAL)

-SULPHURIC ACIDS
- PROPYLENE GAS

UNABSORBED

REACTION OF

SULPHURIC ACID WITH

PROPELYNE GAS-
RECYCLED

PROPYLENE

MIXER CHAMBER-
WATER FEED

FLASH ZONE

SEPARATION

MIXING CHAMBER-
WATER FEED

ACID

IPA
GENERATION

RECONCENTRATION

-RECYCLED

DISTILLATION COLUMN
-ETHER COLUMN
-DRIYING COLUMN

OUTPUT

-DIISOPROPYL ETHER
-ISOPROPYL ALCOHOL IN CDM

AND ANHYDROUS

PROCESS FLOW

DIAGRAM

INDIRECT HYDRATION

METHOD

PROPYLENE
COLUMN
C104

WATER
DIISOPROPYL ETHER

18

28

SODIUM HYDROXIDE
FEED

ENTRAINER

SCRUBBER
C103

C100

21

DECANTER
F101

C102

WASH WATER

DIISOPROPYL
COLUMN
C109

PROPYELENE
FEED

PROPANE

ABSORBER
C100

C101

CONCENTARTED
SULFURIC ACID FEED

22

IPA
GENERATIONS
C102

WATER
LAYER
STRIPPERS
C108

20

ETHER
COLUMN
C105

ALCOHOL
COLUMN
C106

DRYING
COLUMN
C107

STEAM

MIXER
M100

MIXER
M101

CRUDE ISOPROPYL
ALCOHOL TANK
F100

FLASH VESSEL
C101

WATER

SULPHURIC ACID
TO ACID CONTETRATOR

WATER
FEED

WATER

CBM OR
AZEOTROPIC
ISOPROPYL
ALCOHOL

WATER
FEED

12

11

ANHYDROUS
ISOPROPYL
ALCOHOL

V100

P100

Title: PFD study of the Production of Isopropyl Alcohol-indirect hydration method

INITIAL INPUT:-

PRODUCT:-

GROUP MEMBERS:

RAW MATERIALS CONSIST OF

UNIVERSITI
KEBANGSAAN
MALAYSIA

1. ANHYDROUS ISOPROPYL ALCOHOL

1.MOHD AZIZAN BIN RAZAL @ ABD RAZI

I. SULPHURIC ACIDS (60%-70% WT)

2.AZETROPE ISOPROPYL ALCOHOL

2.CHONG KIN HOW

2. PROPYLENE GAS (45% WT)

3. DIISOPROPYL ETHER

3.NORASMANIRA BINTI MUSA

4.NORFATYHAH BINTI ABD AZIZ

National University of Malaysia

NUR IZAYU BINTI BADARUDDIN

PFD DESCRIPTION

STEP 1

Stream 1 (concentrated Sulphuric Acid(60-70
wt%)) + stream 2(Propylene Gases (45wt%))

. Occur in the absorber C100

. Condition for the absorber C100 are:

1. At the pressure 150-300 psig.

2. At temperature 85-115°C.

PROPYELENE
FEED

ABSORBER

C100

CONCENTARTED
SULFURIC ACID FEED

PFD DESCRIPTION

STEP 2

extract liquid in the absorber

Stream 1+ Stream 2

C100.

Extract liquid consist of:-

40 to 65 wt% of Sulphuric Acid,

1.

about 10 to 40 wt% of absorbed Propylene values,
3. balance water,

2.

4. Absorbed propylene-all molecule in the liquid (propyl
(CH), and propylene (CH))

5. IPA at 10-45 wt%,

6. Diisopropyl Ether at 3-6 wt%,

The extract liquid is withdrawn from the bottom portion of
absorber via Stream 3 to the mixer M100.

ENE

ABSORBER
C100

MIXER
M100

PFD DESCRIPTION

STEP 3

Unabsorbed gas- Propylene gas are withdrawn
and compressed to propylene column by c104 via
stream 4.
It will refined- produced recovered Propylene Gas
and some Propane.

• The recovered gas-being recycled by stream 5.

PROPYLENE
COLUMN

C104

SODIUM HYDROXIDE

FEED

SCRUBBER
С109

C100

C102

PROPYELENE

PROPANE

FEED

PFD DESCRIPTION

STEP 4

. In the mixer M100.

Stream 3 mixes with stream 7 which feed with
water.

2. Water is added in an amount from about 1.5 to 6
wt% water, based on the weight of absorbed
Propylene values in the extract liquid.
3. It will make sure the moles of water

stoichiometrically required to form the amount
of Diisopropyl Ether and Isopropyl Alcohol
withdrawn as vapor in the flash vessel C101.

MIXER
M100

FLASH VESSEL

[

C101

W

F

WATER
FEED

PFD DESCRIPTION

STEP 5

Flash vessels C101 is operate in the condition of:-
1. At temperature between 80 to 160ºC.

2. At pressure from about 5 to 10 psig.

The overhead products is withdrawn and being compressed by
C101 via stream 10 comprising :-

1. Diisipropyl Ether from about 30 to 50 wt%,

2. Isopropyl Alcohol from about 30 to 40 wt%,

3. Propylene from about 10 to 20 wt%.

Liquid which is withdrawn from the flash vessel via stream 9
comprises the depleted extract :-

1. Absorbed Propylene - 5 to 35 wt%,
2. Sulphuric acids-45 to 65 wt%,

3. Balance water.

C101

8

FLASH VESSEL

C101

WAT

FEE

PFD DESCRIPTION

STEP 6

⚫ Depleted extract have 2 portions:-

First portion (40 to 60 wt% of total) will be recycled, pump
by P100 through stream 11 and 1 to absorber C100.

A control valve V100 -increase or decrease liquid flow between
stream 11 and 12 and control Diisopropyl Ether and
Isopropyl Alcohol production.

► Second portion is sent to second water mixing zone M101.

WATER
FEED

☑

V100

P100

PFD DESCRIPTION

STEP 7

. The depleted liquids in stream 12 flow to mixer M101.
In the mixer M101:-

Depleted extract mixes stream 13 which feed with water (35
to 100 parts by weight of water per part by weight of

absorbed Propylene Values).

●The liquid residence time in water mixing zone ranges from
about 1 to 30 minutes.

13

MIXER

M101

WATER
FEED

12

PFD DESCRIPTION

STEP 8

The mixture sent via stream 14 to alcohol generator C102
to be heated.

Direct injection steam at stream 15 to generator.

Unit operation for Alcohol generator are:-

1. At temperature about 70 to 130ºC

2. Pressure about 1 to 5 psig

Alcohol vapor are formed as overhead product and sent to
scrubber C103 via stream 17-comprised IPA and Diisopropyl
Ether.

Sulphuric acid about 45 to 55 wt% is withdrawn from lower
portion of alcohol generator to acid concentrator via stream
16.

C102

IPA

GENERATIONS

C102

15

14

STEAM

16

MIXER
M101

SCRUI

ALI

SULPHURIC ACID

TO ACID CONTETRATOR

PFD DESCRIPTION

STEP 9

Product stream 10 mixed with product in stream 17-

flow to the scrubber C103.

Product in scrubber have been neutralized using NaOH at
concentration 10 wt% of the alcohol and Sulphuric mixture.
Unit operation of the Scrubber C103:-

1. At temperature 373K.

2. Pressure 14.7 psi.

The product at 55 wt% IPA is withdrawn from a lower part to
crude isopropyl alcohol tank F100.

From the tank, mixture is sent to ether column C105

18

SODIUM HYDROXIDE

FEED

SCRUBBER

C103

C102

19

C101

IPA

PFD DESCRIPTION
STEP 9-continue

Mixture in F100 will send to ether column C105 via

stream 20.

⚫ Unit operations for Ether column C105 are:-

1. At the temperature 362 K.

2. Pressure 14.7 psi.

Distillation take place to separate Diisopropyl Ether and
Hexene.

Diisopropyl Ether is withdrawn to Diisopropyl Column C109.
Washed to produce washed Ether at 95 wt.%.

PROPYLENE

COLUMN

WATER

C104

DIISOPROPYL ETHER

DE

SCRUBBER

C103

21

8

WASH WATER

DIISOPROPYL
COLUMN
C109

PROPANE

19

22

ETHER
COLUMN

ALCOHOL
COLUMN
С106

20

C105

STEAM

25

CRUDE ISOPROPYL
ALCOHOL TANK
F100

WATER

PFD DESCRIPTION

STEP 10

Wet IPA from Ether column C105 will be send to Alcohol
column C106 via stream 22.

⚫ Unit operation for Alcohol Column C106:-

1. At pressure about 3 to 7 atm.

Azeotroping agent is feed near the top of column C106 via
stream 23 which is produce in drying column C107.

⚫ CBM or azeotropic isopropyl alcohol at 87 wt% is
withdrawn from upper part of alcohol column via stream 24
(product) while water is withdrawn from bottom of column
via stream 25.

WASH WATER

DIISOPROPYL

COLUMN
C109

23

22

ALCOHOL
COLUMNN
C106

24

25

WATER

CBM OR
AZEOTROPIC

ISOPROPYL

ALCOHOL

PFD DESCRIPTION

STEP 11

Unit operation for Drying column C107:-

1. At pressure 14.7 psi.

2. Temperature 347 K.

Product form: Ternery Azeotrope.

Latter concentrate at head column in concentration about 60%
is piped into condenser.

Liquefaction of vapor enter decanter F101 to separate the
layers into virtually water-free upper layer and lower layer
containing the resídual water.

The upper layers in F101 (mainly azeotroping agent and
alcohol) is return to the top of column C107.

While anhydrous Isopropyl Alcohol at 99.8 wt% is removed
from the lower part of column C107 via stream 29.

Ezz

ENTRAINER

DECANTER
F101

WATER
LAYER
STRIPPERS
C108

DRYING
COLUMN
C107

WATER

ANHYDROUS
ISOPROPYL
ALCOHOL

PFD DESCRIPTION

STEP 12

The lower layer in the decanter F101 is mostly water.
It is fed into stripping column C108.

Unit operation for Stripping column C108:-

1. a temperature 466K.

2. pressure about 155 psi.

The waste water in F101 is send to C108 via stream 30
for recovery of Isopropyl Alcohol and azeotroping agent.
This product is send back into column C107 via stream
31 and waste the water at stream 32.

CONCLUSION

☐ The indirect process = Propene with sulfuric
acid to form a mixture of sulfate esters and
subsequent hydrolysis will produce isopropyl
alcohol.

■ Direct hydration = Propene and water, either
in gas or liquid phases, at high pressures in the
presence of solid or supported acidic catalysts

Use of IPA in direct solvent applications accounted for 62% of
total IPA demand in 2008.

Global IPA-based acetone production is expected to decrease
with the increase of phenol capacity (acetone is a coproduct
of phenol by the cumene peroxidation process). Acetone will
be producing after 2010 in Western Europe.

In 2008, global supply/demand was relatively balanced as
demand decreased because of the weakened global economy.

The future demand of IPA is expected to remain flat or to
grow slightly.

Its main usage as a chemical intermediate is growing, and this
should offset the pressure on use as a solvent from tighter
volatile organic chemicals (VOC) regulations

THE END

2. Water is added in an amount from about 1.5 to 6
wt% water, based on the weight of absorbed
Propylene values in the extract liquid.
3. It will make sure the moles of water

stoichiometrically required to form the amount
of Diisopropyl Ether and Isopropyl Alcohol
withdrawn as vapor in the flash vessel C101.


Question: What is the total mass loss rate (in percentage or g/g) from virgin glass batch during melting based on TGA data?

Effect of alumina source on ease of melting of glass batch

David A. Pierce, Pavel Hrma, José Marcial, Brian J. Riley, Michael J. Schweiger

Pacific Northwest National Laboratory, Richland, WA 99354

Abstract

The selection of raw materials affects the rate of batch-to-glass conversion. In all-electric melters,
foam under the batch blanket limits the heat flux from the molten glass, thus slowing the rate of melting.
Our study, in which we compare the melting behaviors of three batches formulated to vitrify high-alumina
high-level waste, shows that a slowly dissolving refractory component can cause excessive foaming.
Faster melting batches with gibbsite [Al(OH)3] or boehmite [AlO(OH)] as an alumina source produced
substantially less foaming than a batch with corundum (Al2O3). While gibbsite and boehmite dissolved
below 500°C, corundum was still present in the batch up to 900°C; hence, the glass-forming melt lacked
alumina in the batch with corundum. The low viscosity of that batch caused the open pores to close
prematurely at 660°C, trapping gases and expanding to foam. This would explain the literature-reported
slow melting rate of a batch with corundum, as compared to batches with gibbsite and boehmite.

Introduction¹

Our study was motivated by the effect of alumina source on the rate of melting observed in [1], a

publicly available report that provides a summary of studies of the effects of composition on the rate of

¹ This work was supported by the U.S. Department of Energy Federal Project Office Engineering Division for the

1

Hanford Tank Waste Treatment and Immobilization Plant.

melting in continuous electric melters of various scales conducted to assess the performance of the

Hanford Waste Treatment and Immobilization Plant currently under construction in Washington State.
For information regarding nuclear waste vitrification, we refer the reader to the review by Vienna [2] and

the literature cited there.

Generally, the selection of batch materials affects the rate of glass melting. In particular, additions
of refractory components, such as crystalline alumina (corundum) [1], zinc oxide [3], or zirconia
(baddeleyite) decrease the rate of melting of glass batches in continuous melters. This effect can be
considerable. Table 1 lists the results of melter experiments with three batches reported in [1]. These
batches were formulated to vitrify a simulated high-alumina high-level waste and each was prepared with
a different alumina precursor: one with gibbsite [Al(OH)3], another with boehmite [AlO(OH)], and the
other with corundum (Al2O3). Table 1 shows that batches with gibbsite and boehmite melted substantially
faster than the batch prepared with corundum.

The list of alumina sources used for commercial glasses is extensive [4]. In nuclear waste glasses,
alumina can be a waste component, typically in the form of gibbsite and boehmite, or a glass-forming
additive. Whereas alumina rarely is a major component in commercial glasses, nuclear waste glass can
contain up to 30 mass % of alumina [5].

The considerable effect of batch materials on the rate of melting has important economic
consequences. The life cycle of high-level waste vitrification at Hanford depends on the rate of melting,
and thus will be affected by the selection of glass-forming and modifying additives used for waste
vitrification. Additionally, the chemical and mineralogical form of waste simulants influences prediction
of the performance of waste-glass melters. Thus, corundum appears a poor substitute for gibbsite and
boehmite, which are common in Hanford high-level wastes.

The very fact that the corundum, or any refractory oxide, slows down the melting of glass is

intriguing because it can hardly be attributed to the refractoriness alone if the residence time of glass in
the melter is long enough to allow a refractory oxide to dissolve and homogenize.

In an all-electric melter, the rate of melting of the batch blanket, or the cold cap, is determined by
the heat flux delivered to the cold cap from the pool of molten glass on which the cold cap floats.
Accordingly, the presence of a refractory oxide, such as corundum, must affect the heat transfer to or
within the cold cap.

Indeed, laboratory examination revealed that the batches with corundum produced copious foam
whereas the batches with gibbsite did not [6, 7]. Foam accumulated under the cold cap insulates the cold
cap from the melt, thus reducing the heat flow to the cold cap [8-11]. The intriguing question is about the
mechanism by which corundum, a stable oxide that does not participate in any gas-evolving reaction,
intensifies foam accumulation.

Two types of foam are associated with glass melting. Primary foam, term coined by Gerrard and
Smith [12], is batch expansion caused by the evolution of batch-reaction gases, such as CO2, after enough
glass-forming melt was produced in the batch to close the open pores. Secondary foam is generally a term
reserved for foam created in molten glass from fining-reaction gases [12, 13]. In high-level-waste glass
melts, secondary foam results from oxidation-reduction reactions, mainly involving ferric oxide. Neither
foam is directly associated with the dissolution of corundum in molten glass.

This study employs several experimental techniques to compare the melting behavior of three
high-alumina batches with identical compositions except for sources of alumina. It is focused on the
difference between batches containing corundum and gibbsite, although experiments were also performed
with a batch containing boehmite. As argued in the Discussion section, excessive foaming of the

corundum-containing batch can be attributed to the early closure of open pores caused by the low
viscosity of the glass-forming melt.

Experimental Approach

Table 2 shows the composition of a batch used in previous studies [10, 14] with gibbsite, Al(OH)3
(Almatis, Lot No. 0724131923), as the alumina source. The other two batches examined in this study
contained equivalent fractions (g per g glass) of corundum (Sigma-Aldrich®, Lot No. 342688) and
boehmite (Nabaltec, Lot No. 047235), i.e., 0.240 of Al2O3 and 0.280 of AlO(OH). Fractions of all other
components remained identical. All batches were made with quartz particles of 75 μm as the source of
silica. The particle size of corundum, by image analysis, was 45.6 ± 8.6 μm. The glass composition, in
terms of targeted mass fractions, was SiO2 (0.305), Al2O3 (0.240), B2O3 (0.152), Na₂O (0.096), CaO
(0.061), Fe2O3 (0.059), Li₂O (0.036), Bi₂O3 (0.011), P2O5 (0.011), F (0.007), Cr2O3 (0.005), PbO (0.004),
NiO (0.004), ZrO2 (0.004), SO3 (0.002), K₂O (0.001), MgO (0.001), and ZnO (0.001). As described
elsewhere [14], batches were prepared as slurry and were dried at 105°C overnight in an oven.

To measure the expansion of a batch during heating, ~1.5 g of batch was pressed at ~7 MPa into a
cylindrical pellet ~13 mm in diameter and ~6.5 mm high. Each pellet was placed into a Deltech® (Denver,
CO, U.S.A) furnace with a silica-glass viewing window and heated at 5°C/min on an alumina plate to
1000°C. Pellets were photographed at regular intervals, and their profile areas were measured with

Ⓡ

Photoshop (Adobe®, San Jose, CA, U.S.A.). Next to the pellet was a Pt wire, 10-mm in length, which

was used as a scale gauge. The profile area, A, was normalized to the profile area of a hemispherical body
of the glass, i.e., to A₁ = (9π/32)¹/³ (mpl.fpg)²/³ = 0.9596(mølfp₂) 2/³, where mp is the initial pellet mass,

2/3

s, fis the

batch mass fraction per glass, and pg is the glass density.

For X-ray diffraction (XRD) and microscopy examinations, approximately 10-g samples were
heated at 5°C/min to temperatures of 400 to 1200°C in either a porcelain crucible (samples heated to
<700°C) or Pt/10%Rh crucibles (samples heated to 800 to 1200°C) and air quenched. Each sample was
weighed before and after the heat treatment. Half of the specimens were powdered and mixed with

~5 mass% CaF2 as an internal standard for XRD. The other half of specimens, heat treated to 1100 and
1200°C, were used to make thin sections for optical microscopy.

XRD was performed with a BrukerⓇ D8 Advance diffractometer (Bruker AXS Inc., Madison,
WI) equipped with a Cu Ka target at a power level of 40 kV and 40 mA. The instrument utilized a
LynxEyeposition-sensitive detector with an angular range of 3° 20. The mass fractions of crystalline
phases were obtained from XRD patterns with Jade® and RIQAS® software (MDI, Livermore, CA,
U.S.A.).

Optical microscopy on samples heat-treated to 800 to 1200°C was performed with OlympusⓇ
(Center Valley, PA, U.S.A.) SZH10 and PMG-3 microscopes. Samples of batches containing corundum
and gibbsite, heated to 600 and 700°C, were viewed with a JEOL® (Akishima, Tokyo, Japan) 5900
scanning electron microscope (SEM) and analyzed with an EDAX® (Mahwah, NJ, U.S.A.) lithium-drifted
silicon energy-dispersive X-ray spectrometer (EDS). Since the samples were not fully sintered, they were
cast in an epoxy resin and polished to an optical quality finish before analysis.

Finally, batch samples, ~20 to 50 mg, were analyzed with TA Instruments' (New Castle, DE,
U.S.A.) SDT Q-600 for thermo-gravimetric analysis (TGA).

Results

From TGA, the total mass losses on melting were -0.27 g/g glass for the gibbsite batch, ~0.17 g/g
glass for the boehmite batch, and ~0.15 g/g glass for the corundum batch, roughly corresponding to the
different content of water in the alumina sources, but were slightly smaller than those obtained from the
stoichiometry of the batched chemicals—see Table 3. As seen in Figure 1, the peak heights and positions
in the TGA plots reveal large differences in gas-releasing reactions between batches that differ solely in
the alumina source. Further investigation of these reactions and associated off-gas is presently underway.

Figure 2 displays photographs of the cylindrical pellets taken at specific temperatures and

Figure 3 shows the plots of the normalized profile area, A/Ag, against temperature. After mild gradual
expansion, the batch with corundum shrank starting at ~600°C, reached a minimum profile area at
~650°C, and then rapidly expanded to more than twice the minimum profile area at -850°C (see also
shrinking and expansion of pellets in Figure 2). Unlike the pellet with corundum, the pellet from the batch
with gibbsite maintained a nearly constant profile area until it shrank at ~700°C, reaching a minimum
profile area at ~800°C. The pellet profile area then began to increase, becoming ~40% larger at ~950°C
than the minimum profile area. The pellet from the batch with boehmite responded to heating similarly to
the batch with gibbsite except that both the minimum and maximum profile areas occurred at -50°C
lower temperatures. All pellets finally collapsed to a bubbly glass that spread over the alumina support
plate.

Figure 4 shows the undissolved quartz and corundum fractions versus temperature, in which
arctangent trend lines were fitted to the data. A notable difference in the extent of quartz dissolution can
first be seen at ~400°C where the batch containing corundum has lost -20% of the initial quartz while
batches with gibbsite and boehmite lost <10%. The first derivatives of the arctangent trend lines, Figure 5,
show that the temperature of the maximum rate of quartz dissolution increased in the order corundum-
gibbsite-boehmite; the maximum rate of dissolution also slightly increased in that order, just enough for
the quartz to be fully dissolved at around the same temperature in all batches.

Corundum dissolved rapidly between 700 and 1000°C. Hence, corundum had remained inert up
to ~700°C. In contrast with corundum, gibbsite and boehmite could not be detected by XRD (Figure 6)
even at temperatures as low as 500°C. Boehmite was only detected at temperatures ≤ 400°C in both
gibbsite and boehmite batches. Immediately after the boehmite disappeared at 500°C, nepheline was
produced and existed up to 900°C in the feed with gibbsite, and up to 800°C in the feed with boehmite.

Sodalite was produced in batches within the range of 500°C (600°C in the feed with corundum) to
1000°C. In all three batches, hematite was present up to ~1000°C whereas spinel formed at 900°C.

Quartz and corundum particles can be seen in SEM micrographs, Figure 7. At 600°C, the
corundum particles are seen in region b of Figures 7A and 7B. Grayish regions, (a in Figures 7A and B,
and c and d in Figure 7C) are rich in Fe2O3. The round dark object, region a, Figure 7C (the gibbsite
batch, 700°C), is a quartz particle surrounded by a thin diffusion layer.

Optical micrographs, Figure 8, show sections of melts from batches with corundum and gibbsite
heated to 1100 and 1200°C. At 1100°C, the melts somewhat differ in the size and distribution of bubbles

and appear fairly similar in homogeneity. Dark regions contain tiny crystals of spinel (magnetite). At
1200°C, all bubbles are gone and the crystals are nearly uniformly distributed within each melt.

Discussion

The alumina source substantially influences batch behavior throughout the whole temperature
interval of the batch-to-glass conversion, including the early stages. Reactions between waste components
and additives occur as soon as they are mixed in the slurry and then during drying, as the differences
between as-batched and dried masses, listed in Table 3, indicate. These reactions include those between
acids and bases (NaOH and H3BO3), formation of solid solutions of salts, and interactions of aluminum
hydroxide and oxyhydrate with dissolved components. However, the important differences between the
behaviors of batches with gibbsite or boehmite and that of the batch with corundum occur during the heat
treatment. These differences influence the initial gas-evolving reactions (Figure 1), the kinetics of quartz
dissolution (Figures 4 and 5), the volume expansion or foaming (Figures 2 and 3), and the formation and
motions of bubbles (Figure 8).

The initial gas-evolving reactions and the kinetics of quartz dissolution are related through the

generation of glass-forming melt in a process that influences volume expansion (foaming) [10, 14, 15,
16]. The initial reactions evolve the chemically bonded water from salts, hydroxides, oxyhydrates, and
acids. Nearly simultaneously with these reactions, the oxyionic salts produce eutectic melts, the borates
generate the first glass-forming melt, and the hydroxides and oxyhydrates become amorphous oxides,
mainly Al2O3, but also a portion of Fe2O3 (the other portion becomes hematite). Amorphous oxides, in
turn, dissolve in both molten salts and molten borates. The addition of Al2O3 to the borate melt
considerably increases its viscosity [17].

The batch melting reactions are numerous and complex. Therefore, it is difficult to identify the
chemistry of various overlapping TGA peaks seen in Fig. 1. By stoichiometry, the gases released by early
reactions from the gibbsite-containing batch (Table 1) are H₂O (1.20×10³), CO₂ (94), NO (14), and O₂ (9);
the numbers in parentheses show m³ of gas per kg of glass at 630°C. Most of these gases are released
from reactions between components rather than by simple decomposition of hydroxides and salts. The
peak at ~130°C in the corundum-containing batch can possibly be attributed to borax, a reaction product
of NaOH and HBO3; the peak is missing in the other two batches, where NaOH had possibly reacted
with gibbsite and boehmite to form sodium aluminate.

Both melts, ionic and covalent, attack quartz particles [16]. Alkali nitrates and carbonates react
with quartz to form alkali silicates that fuse with the borate melt. While the borate melt dissolves quartz
directly, it also protects it from molten salts. The alumino-borate melt occupies more space (there is 24
mass% Al2O3 in the final glass) and is more viscous, hence less aggressive, than the melt without alumina
in the corundum-containing batch. This may explain why <10% of quartz was dissolved in the batches
containing gibbsite or boehmite at 400°C, whereas more than twice as much quartz was dissolved in the
batch containing corundum.

As we argue below, a lower viscosity of the glass-forming melt in the corundum-containing batch
may also be responsible for the earlier closure of pores, i.e., the lower temperature at which the batch

volume reaches a minimum. The rapid expansion that follows the minimum volume indicates that the
glass-forming melt has become connected, i.e., the open porosity, through which evolving gases were
escaping freely to the atmosphere, has closed. The connected melt presents a barrier to gases trapped in
bubbles, which cannot escape because the melt viscosity is high. If the porosity becomes closed at a
temperature at which the batch gases are still evolving, the growing bubbles change the bubbly melt into
primary foam. Primary foam expands to cellular foam and eventually collapses internally into large
cavities that burst into the atmosphere because of the increasing internal pressure and decreasing melt
viscosity as the temperature continues to increase [10, 15].

The temperature at which the glass-forming melt becomes connected determines whether primary
foam will occur in the batch. The batch with corundum shrank to a minimum volume—the point at which
glass melt became connected—at a temperature of 660°C, whereas the batch with boehmite reached the
minimum volume at 750°C and the batch with gibbsite at 810°C (Figure 3). In borosilicate waste glasses,
the gas-evolving batch reactions are complete by 700 to 800°C, typically by 750°C [18-20]. The crucial
point is that if the melt from the batch with corundum became connected while batch gases were still
evolving, copious primary foam was the result; whereas the melts from the batches with gibbsite and
boehmite released the batch gases without producing primary foam.

As hinted above, the cause of the early closure of open porosity in the batch with corundum
appears associated with the delayed incorporation of alumina into the glass-forming melt. Factors that
influence the temperature at which the glass-forming melt becomes connected are the volume fraction of
the melt (the melt-solid ratio) and the viscosity [10]—a tricky concept because the melt is far from
homogeneous at this stage. We can assume that in the batches with gibbsite and boehmite, the melt with a
higher alumina content, though with a somewhat lower silica content, had a higher viscosity, and thus
moved more slowly, allowing the pores to close at a higher temperature.

The other source of bubbles, the redox or fining reactions (and also the decomposition of

sodalite-

-see Figure 6), produce secondary foam, to which the volume expansion in batches with gibbsite

and boehmite can solely be attributed. In the melt from the batch with corundum, secondary foam was

produced before primary foam could collapse. Thus, in the batch with corundum, the transition from
primary foam to secondary foam was continuous.

Though expansion from primary foam in the melt can be avoided by an appropriate choice of the
chemical form of batch components, the presence of secondary foam is inevitable. In the glass melts
under study, secondary foam results from oxidation-reduction reactions, mainly involving ferric oxide
[21]. These reactions are initially suppressed by nitrates, which are strong oxidizing agents. After nitrates
are gone above 750°C, redox reactions reach equilibrium with oxygen in bubbles. The oxidation-
reduction equilibria depend on the temperature and the melt basicity. As temperature increases, the
equilibria shift to the reduced state and oxygen is liberated. Silica from dissolving quartz decreases melt
basicity [22], thus contributing to the secondary foam development by shifting iron redox equilibria in the
direction of oxygen release.

Other contributing factors are dissolution and precipitation of iron-containing crystalline phases.
As has been suggested by Henager et al. [15], the dissolving hematite and the precipitating spinel may
help accelerate the evolution of oxygen from the redox reaction 2 Fe2O3(m) → 4 FeO(m) + O2(g), where
m and g denote the melt and gas phase, respectively. Dissolving hematite supplies Fe2O3 to the melt by
the reaction Fe2O3(c) → Fe2O3(m), where c denotes the crystalline phase. At the same time, FeO reacts
with Fe2O3, precipitating magnetite by the reaction FeO(m) + Fe2O3(m) → Fe3O4(c), which removes FeO
from the melt. Both reactions, dissolving hematite and precipitating magnetite, shift the oxidation-
reduction reaction to the right, thus promoting oxygen evolution, and consequently secondary foaming.

The fact that the slow-melting batch with corundum (see Table 1) generated massive primary
foam, whereas the faster-melting batches with gibbsite did not, indicates that primary foam is likely a
major cause of slow melting of glass batches. Secondary foam is less detrimental because it can be swept
away by convection currents, especially by forced convection (bubbling), from the cold cap bottom to the
free surface of the melt, where it can collapse or accumulate. The faster melting of the batch with

boehmite as compared to that with gibbsite remains unexplained. Attributing it to the smaller content of

water in boehmite seems somewhat speculative.

The differences in amounts and sizes of bubbles between the melts at 1100°C (Figure 8) are
probably associated with the melt homogeneity. In a less homogeneous melt, bubbles pass through less
viscous portions that are likely to be connected, because high-viscosity inhomogeneities surround the
dissolving silica and alumina grains. This may account for the presence of large bubbles in the melt from
the batch with gibbsite. Photographs of samples taken at 1200°C indicate that melts from all three batches
were nearly equally homogeneous at this temperature. The streaks, barely visible in the images, were
caused by convection. Two sources of natural convection operate in crucible melts. Convection driven by
surface tension gradients results from Na2O and B2O3 volatilization in the meniscus area. These currents
bring the melt to the surface where the ferrous-ferric ratio is altered by the diffusion of oxygen from the
melt to the atmosphere, resulting in a change of phase equilibria between the melt and submicron iron-
containing crystals (mostly magnetite). This change is reflected in the change of color that makes the
streaks visible. The other source of streaks is associated with silica-rich inhomogeneities stuck to the
crucible bottom. These inhomogeneities, some containing residues of quartz particles, have high viscosity
and do not contain spinel crystals, which makes them transparent. Gas bubbles nucleate around them and
drag the inhomogeneities upward to the melt surface. A typical example of this effect is shown in Figure

9.

The results of this study support our initial hypothesis that the slow melting of the batch with
corundum is caused by foam generation. Nevertheless, the batch-to-glass conversion process described in
this section, though plausible, is hypothetical in various aspects. Hopefully, it will inspire research into
diffusion processes that occur in the glass-forming melt. From a technological point of view, the set of
simple tests used in this study may allow preselecting batches for conducting more expensive scaling-up
experiments.

Conclusion

The alumina source in otherwise identical glass batches affects the reaction sequence during
melting, the kinetics of quartz dissolution, and, most notably, the batch expansion. The batch with
corundum exhibited ample primary foam, which was absent in batches prepared with gibbsite and
boehmite. Excessive foaming of the batch with corundum was most likely caused by an early closure of
open pores by the glass-forming melt that had a low viscosity because most of the alumina was still
undissolved when the pores were closing. The lower production rate when a batch containing corundum
was processed in a continuous electric melter can thus be attributed to the extensive foaming caused by
the late incorporation of alumina into the glass-forming melt.

Acknowledgements

The authors are grateful to Albert Kruger for his assistance and guidance and to Dong-Sang Kim
for his help and insight in weekly meetings as well as Mark Steward for his contributions. Pacific
Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract

DE-AC05-76RL01830.

References

1. K. S Matlack., H. Gan, M. Chaudhuri, W. Kot, W Gong, T. Bardakci, I. Pegg, and J. Innocent,
DM100 and DM1200 melter testing with high waste loading glass formulations for Hanford high-
aluminum HLW streams, VSL-10R1690-1, Vitreous State Laboratory, Washington DC, 2010.

2. J. D. Vienna, Nuclear waste vitrification in the United States: Recent developments and future

options, Int. J. Appl. Glass Sci. 1 [3] 309-321 (2010).

3. H. H. Russell III, W. R. Ott, “The effect of batch preparation on some zinc opal glasses," Glass

Technol. 21, 237-243 (1980).

4. F. V. Tooley, The handbook of glass manufacture, Vol. I, p. 24, Books for Industry, New York, 1974.
5. J. D. Vienna, A. Fluegel, D. S. Kim, P. Hrma, Glass Property Data and Models for Estimating High-
Level Waste Glass Volume, PNNL-18501, Pacific Northwest National Laboratory, Richland,
Washington, 2009.

6. P. Hrma., M. J. Schweiger, C. J. Humrickhouse, J. A. Moody, R. M. Tate, N. E. TeGrotenhuis, B. M.
Arrigoni, and C. P. Rodriguez, “Effect of melter-feed-makeup on vitrification process,” 2009ISRSM,
Proceedings of International Symposium on Radiation Safety Management, Daejeon, Korea, 280-290,

2009.

7. D. A. Pierce, P. Hrma, and M. J. Schweiger, “Effect of alumina source on HLW-feed melting
process,” Proceedings of Materials Science and Technology 112th Ann. Meeting, CD-ROM, Amer.

Ceram. Soc. and ASM Intern. 2010.

8. P. Hrma, “Melting of foaming batches: nuclear waste glass," Glastech. Ber. 63K, 360-369 (1990).

9. J. Kloužek, M. Arkosinová, L. Němec, and P. Cinibusová “The Role of Sulphur Compounds in Glass
Melting," Eur. J. Glass Sci. Technol. A 48, 176 (2007).

10. P. Hrma, M. J. Schweiger, C. J. Humrickhouse, J. A. Moody, R. M. Tate, T. T. Rainsdon, N. E.
TeGrotenhuis, B. M. Arrigoni, J. Marcial, C. P. Rodriguez, and B. H. Tincher, “Effect of glass-batch
makeup on the melting process,” Ceramics-Silikaty 54, 193-211 (2010).

11. R. Conradt, P. Suwannathada, and P. Pinkhaokham, “Local temperature distribution and primary melt
formation in a melting batch heap," Glastech. Ber. 67, 103 (1994).

12. A. H. Gerrard and I. H. Smith, “Laboratory techniques for studying foam formation and stability in
glass melting," Glastech. Ber. 56K, 13-18 (1983).

13. J. Kappel, R. Conradt, and H. Scholze, “Foaming behavior in glass melts." Glastech. Ber. 60, 189-

201 (1978).

14. M. J. Schweiger, P. Hrma, C. J. Humrickhouse, J. Marcial, B. J. Riley, and N. E. TeGrotenhuis,

"Cluster formation of silica particles in glass batches during melting," J. Non-Cryst. Solids 356 [25-
27] 1359-1367 (2010).

15. S. Henager, H., P. Hrma, K.J. Swearingen, M. J. Schweiger, J. Marcial, and N. E. TeGrotenhuis,
"Conversion of batch to molten glass, I: Volume expansion,” accepted in J. Non-Cryst. Solids.

16. P. Hrma, K. J. Swearingen, S. H. Henager, M. J. Schweiger, J. Marcial, N. E. TeGrotenhuis,
Conversion of batch to molten glass, II: Dissolution of quartz particles, J. Non-Cryst. Solids. 357,
820-828 (2011).

17. P. Hrma, B. M. Arrigoni, M. J. Schweiger, “Viscosity of many-component glasses”, J. Non-Cryst.
Solids 355 [14-15] 891-902 (2009).

18. J. G. Darab, E. M. Meiers, and P. A. Smith, “Behavior of Simulated Hanford Slurries During
Conversion to Glass," Mat. Res. Soc. Proc. 556, 215-222 (1999).

19. P.A. Smith, J.D. Vienna, and P. Hrma, “The Effects of Melting Reactions on Laboratory-Scale Waste
Vitrification," J. Mat. Res., 10 [8] 2137-2149 (1995)

20. P. Hrma, J. Matyáš, and D.-S. Kim, “The Chemistry and Physics of Melter Cold Cap,” 9th Biennial
Int. Conf. On Nucl. And Hazardous Waste Management, Spectrum '02, American Nuclear Society,
CD-ROM (2002).

21. H. D. Schreiber, C. W. Schreiber, M. W. Riethmiller, J. S. Downey, “The Effect of Temperature on
the Redox Constraints for the Processing of High-Level Nuclear Waste into a Glass Waste Form,"
Materials Research Society Symposium Proceeding, 176, 419–426 (1990).

22. J. A. Duffy, F. G. K. Baucke, “Effect of glass composition and basicity on reduction of metal ions to

the metallic state in melts,” Phys. Chem. Glasses 38 [1] 25-26 (1997).

Figure captions

Figure 1. Mass-loss rates and mass loss per unit mass of glass (inset) of batches as functions of

temperature.

Figure 2. Photographic images of pressed pellets during heating.

Figure 3. Normalized profile areas of pellets versus temperature.

Figure 4. Fractions of undissolved quartz and corundum versus temperature. The coefficients of
determination (R²) and the standard errors (s) are: R² = 0.977 and s = 0.062 for quartz in batch with
corundum; R² = 0.996 and s = 0.029 for quartz in batch with gibbsite; R² = 0.991 and s = 0.047 for quartz

in batch with boehmite; R² = 0.983 and s = 0.067 for corundum.

Figure 5. Dissolution rate of quartz and corundum versus temperature.

Figure 6. Crystalline fractions of aluminum-containing crystalline phases in batches.

Figure 7. SEM micrographs and EDS of batches with corundum at 600°C (A) and 700°C (B), and with gibbsite at
700°C (C).

Figure 8. Optical images of thin sections of melts from corundum- and gibbsite-containing batches

heated in Pt crucibles at 5°C/min.

Figure 9. Optical micrograph of a melt heated to 1200°C at 5°C/min in a Pt crucible. The streaks trace
circulation flow typical for the meniscus area on the left. Bright spots at the bottom are high-silica
inhomogeneities stuck to the Pt surface. A rising bubble dragging the melt in its wake, while stretching
and thinning the inhomogeneities, as can be seen on the right.

Table 1. Steady state rate of melting in a small electric melter equipped with bubbling [1]

Rate of melting
g/m²/s

W(a)

Al source

Fraction

1150°C

1200°C

Al2O3

0.436

15

11

16

Al(OH)3

0.436

11

Al(OH)3
AIO(OH)

0.450

17

0.450

19

14

(a) W is the mass fraction of glass components from the waste

Table 2. Composition of batch with gibbsite in g per g of glass.

Compound

Fraction

Al(OH)3

0.368

SiO2

0.305

H3BO3
NaOH

0.270

0.099

Li2CO3
Fe(OH)3

0.088

0.074

CaO

0.061

NaF

0.015

Bi(OH)3

0.013

Fe(H2PO2)3

0.012

0.011

Na2CrO4

0.006

Zr(OH)4.H₂O

NiCO3

0.006

Pb(NO3)2

0.006

Na2SO4

0.004

Zn(NO3)2*4H2O

0.003

0.003

KNO3
NaNO2

0.003

Mg(OH)2
Na2C2O4

0.002

0.001

Total

1.350

Table 3. Batch-to-glass ratios.

Batch-to-glass mass ratio

Difference

Dried (b)

As batched (a)

Al source

Al2O3

1.223
1.350

1.150

0.073

1.272

Al(OH)3
AlO(OH)

0.078

1.170

1.260

0.090

(a) Mix of batch chemicals as weighed.

(b) As determined by TGA.

0.016

1.30

1.25

Mass Fraction per Glass

0.014

1.20

1.15

0.012

1.10

Rate, Mass% s-1

0.010

1.05

1.00

0.008

0

200

400

600

800

1000

1200

Temperature, 'C

0.006

Batch with Al2O3

0.004

Batch with Al(OH)3
Batch with AIO (OH)

0.002

0.000

200

800

0

400

600

1000

1200

Temperature, °C

Figure 1.

400°C

800°C

900°C

1000°C

100°C

650°C

Batch with

Al2O3

Batch with

Al(OH)3

Batch with

AIO(OH)

Figure 2.

3.0

2.8

2.6

Batch with Al2O3
Batch with Al(OH)3
Batch with AIO(OH)

Normalized Area, A/A,

2.4

2.2

2.0

1.8

1.6

1.4

1.2

400

0

100

200

300

500

600

700

800

900

1000

Temperature, °C

Figure 3.

1.0

A Quartz in batch with Al2O3
Quartz in batch with Al(OH)3

◆ Quartz in batch with AIO(OH)
O Corundum in batch with Al2O3

0.8

Undissolved Fraction

0.6

0.4

0.2
12

0.0

1200

200

400

600

800

1000

Temperature, °C

Figure 4.

0.012

d

Quartz in Batch with Al2O3

a

0.010

Quartz in Batch with Al(OH)3
Quartz in Batch with AIO(OH)

b

C

Dissolution Rate, K-1

d Corundum in Batch with Al2O3

0.008

0.006

0.004

b

a

0.002

0.000

200 300

1100 1200

400

500

600 700 800

900

1000

Temperature (°C)

Figure 5.

0.40

Batch with Al2O3

0.35

Crystalline Fraction

0.30

0.25

0.20

Corundum

― Sodalite

0.15

0.10

0.05

0.00

400

500

600

700

800

900

1000

Temperature, °C

0.40

Batch with Al(OH) 3

0.35

Crystalline Fraction

0.30

0.25

Boehmite

Nepheline

0.20

➡. Sodalite

0.15

0.10

0.05

0.00

600

400

500

700

800

900

1000

Temperature, °C

0.40

Batch with AIO(OH)

0.35

Crystalline Fraction

0.30

Boehmite

0.25

- Nepheline

0.20

Sodalite

0.15

0.10

0.05

0.00

400

700

800

1000

600

500

900

Temperature, °C

Figure 6.

A

90
80
70
60
40
30
20
10
0
822882222°
100

■a

b

с

Mass%

PbO

εοτιν

CaO

Cr203

Fe203

Na20

MgO

SiO2

ZrO2

ZnO

P205

X1,000

10μm

Z0kU

12 42 AUX

Compounds

B

90
80
70
60
82822322 0
100
30
20
10

Па

■b

Mass %

a

Na20

SiO2

ZrO2

PbO

Fe203

MgO

A1203

P205

Cr203

ZnO

CaO

ZOKU

X750 20μm

12 40 AUX

Compounds

0
883 2 3 2 2 °
100
90
80
40
30
20
10
70
60
50

C

a

■a

пь

口

Mass %

Пс

d

■d

εοτιν

P205

ZrO2

PbO

Bi203

Cr203

Fe203

MgO

SiO2

ZnO

Na20

CaO

20kU

12 40 AUX

X500 50Mm

Compounds

Figure 7.

Batch with Al(OH)3

Batch with Al₂O3

1100°C

mm

1 mm

1200°C

1 mm

1 mm

Figure 8.

1 mm

Figure 9.

From TGA, the total mass losses on melting were -0.27 g/g glass for the gibbsite batch, ~0.17 g/g glass for the boehmite batch, and ~0.15 g/g glass for the corundum batch, roughly corresponding to the different content of water in the alumina sources, but were slightly smaller than those obtained from the stoichiometry of the batched chemicals

Metal, mineral, plastic & glass products


Question: What are the tin loss rates to sludge in electrolytic tinning processes?

Centro Sviluppo

Techint Technologies

THE Materiali S.p.A.

tin lost vs. dissolved tin). The electrolyte is satu-
rated with pure oxygen by means of a system for
oxygen dissolution designed and realized to this
purpose.

TECHINT INSOLUBLE

ANODES

TECHNOLOGY WITH AN

IM-

PROVED TIN

DISSOLUTION

PROCESS.

Interesting results were achieved on the PSA elec-
trolyte. After dedicated tests looking for the best
process parameters, finally the sludge produced by
the process was less than 4 % as tin lost vs. dis-
solved tin. The tin dissolution rate can be easily
controlled by setting the oxygen flow properly.

G. Astengo); Ferrari(2)
1. Techint Technologies, Torre Shipping, Via De Marini
53 16149 Genova, Italy
2. Centro Sviluppo Materiali, Via di Castel Romano 100-
00128 Roma, Italy.

Further trials carried out on a pilot dissolution reac-
tor at CSM laboratories showed that the process is
insensitive to the type of tinplating electrolyte. In
fact, there were no significant differences between
the amounts of sludge generated with phenol-
sulphonic acid (PSA) either with addition of DI-
PHONE or ENSA, and methansulphonic acid
(MSA).

ABSTRACT

The application of Techint insoluble anode technol-
ogy in new or existing tinning lines brings consider-
able benefits in tinplating such as:

minimizing the amount of sludge and hence
the loss of tin;

The pilot plant was able to produce more than 4
kg/h of dissolved tin.

reduction of manpower for anode handling
improved coating quality

better process control

The trials were carried out at different dissolution
rates and with different electrolytes, monitoring the
total amount of generated sludge, the consumptions
of the additives and the quality of tinplate by the
Hull cell test.

elimination of phenol vapors inside the
building.

-

The paper describes into details such improvements
as well as the very satisfactory results reached in
tinplate produced with insoluble anodes. In fact,
with conventional electroplating technology the
homogeneity of tin coating thickness decreases as
the coating weight decreases, due to the particular
geometry of the tin anodes and due to non-uniform
consumption of tin bars.

These successful tests demonstrate that Techint in-
soluble anodes technology is applicable either in
new or existing tinning lines whatever is the type of
electrolyte used.

INTRODUCTION

The critical point of the process is the high produc-
tion of sludge in the present tin dissolution systems
used in the electrotinning lines with insoluble an-
odes. The tin lost in sludge is higher than 10% of
the dissolved tin. This is the reason why the tinplate
process with insoluble anodes is not yet used
worldwide.

Techint has recently developed and realised two
modern and fast tinning lines. The Basic design pa-
rameters are summarized in Table 1.

The ETL/TFSL are capable of tin coating from 1.12
g/m² to 11.2 g/m². All combinations of differential
coatings from 1.12 / 2.24 g/m² to 8.4 / 11.2 g/m² are
producible.

Because of that, Techint Technologies, a division of
TECHINT Group, and its connected Research Cen-
ter, Centro Sviluppo Materiali (CSM) have devel-
oped a new low-sludge tin dissolution process suc-
cessfully proven through extensive tests on Siderar's
tinning line (Argentina).

The most common product of the equal coating per
side is 2.8 / 2.8 g/m². The most common differential
coated strip is 2.8/8.4 g/m². Lower tin coatings
<1.12 g/m² are also feasible.

The process is based on the oxidation of metallic tin
granules by the tinning electrolyte flowing in a dis-
solution reactor, which has well defined process and
technological settings to reduce sludge under 4% (as

The process is based on the use of soluble anodes
and either PSA or MSA baths. Anyway, Techint and
CSM are making considerable efforts to develop the
insoluble-anode technology provided with an im-

Pag. 1/10

File Name: Paper_rev2.docPaper_rev2.doc

Centro Sviluppo

Techint Technologies

T Materiali S.p.A.

proved tin dissolution process able to produce very
low amount of sludge.

increase of tin concentration in the plating solution
is unavoidable with the use of tin anodes, and dilu-
tion of the solution generates overflow and dis-
charge, with loss of expensive material and possible
water pollution, unless adequately treated.

BASIC DESIGN PARAMETERS

Electrolyte: either

Phenol sulphonic acid
(PSA)
Methane
Acid (MSA)

The conventional equipment used worldwide for the
removal of excess tin is the insoluble anode and
many customers today have one half cell equipped
with insoluble anodes, but the control of the solu-
tion is very difficult and concerns about a rapid de-
crease of tin and an increase of free acid in the plat-
ing solution make the use of insoluble anodes in this
way less practical. Other disadvantages with the
Ferrostan process are the fumes exiting the plating
tanks, the labour requirements for handling the tin
anodes and the low productivity.

Sulphonic

or

Production Capacity
Tinplate:

200,000 t/y and over
depending on the mix

TFS:

50,000 t/y
250,000 t/y

Total:

Line Reference Length

140 m

Material Specification

Additionally, market demand is towards tinplate
with thinner coatings; indeed for some uses tin coat-
ings down to 0.2-0.4 g/m² are required, causing
production problems.

0.10 to 0.60 mm

Thickness:

508 to 1250 mm
25,000 kg maximum
up to 2100 mm

Width:

Coil Weight:

Coil OD:

With conventional electroplating technology the
homogeneity of tin coating thickness decreases as
the coating weight decreases, due to the particular
geometry of the tin anodes, which do not present a
continuous surface. In fact, each anode is formed by
a series of vertical bars drawn against each other so
as to leave only a minimum space between the bars,
which may produce a lower tin thickness.

Line Speeds

Entry & Exit Sections:
Process Section:

700 m/min maximum

550 m/min maximum
450 m/min maximum
for TFS

30 m/min

Threading Speed:

Exit Section Shear Speed: 120 m/min maximum

Coating Thickness Range (per side)

11.2 g/m² maximum
1.12 g/m² minimum
100 mg/m² maximum
30 mg/m² minimum
25 mg/m² maximum
10 mg/m² minimum

Tin Coating:

Another cause of irregular tin coating derives from
non-uniform consumption of tin bars, which in turn
gives rise to preferential current distribution. For
thicker coatings such situations are alleviated since
more cells are employed in the sequence of electro-
plating steps, thus allowing the tin coating to grow
more uniformly. In thin coatings this will not be al-
lowed anymore; for instance, in tinplate for the fab-
rication of two-piece DWI cans where, owing to
wall ironing, the tin coating is reduced and could
disappear in those areas where the coating thickness
is not homogeneous.

Chrome Coating as Metal

Chrome as Oxide:

Oil Type

DOS and ATBC
2.5-20 mg/m²/side

Table 1 - Design parameters of ETL/TFS line

The Ferrostan process, based on the use of soluble
tin anodes in Phenolsulphonate solution, is well
consolidated in electro tinning lines. The use of
soluble anodes is advantageous because the tin
plated-out on the strip can be automatically pro-
duced by the dissolution of tin from the anodes; but
there are disadvantages.

One solution to these problems is to equip an entire
tinning line with insoluble anodes, the anode then
has a continuous surface and very thin tin coating
layers can be produced with high thickness homo-
geneity.

The main advantages of tin-plating with insoluble
anodes are summarized in table 2.

The most important one is the necessity to drain off
the plating solution because of the different electro-
chemical efficiency in plating and dissolution. An

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TECHINT

Nevertheless, the use of non-soluble anodes still re-
quires a tin dissolution reactor, connected to the
electro tinning line to replenish the amount of tin
deposited on the strip.

MECHANISM OF DISSOLUTION DEPOSI-

TION PROCESS

The process is based on the oxidation of metallic tin
granules in the tinning electrolyte saturated with
pure oxygen.

Considerable research was done to dissolve tin
(chemically or electrochemically) in the plating so-
lution [1-10]. An industrial process was set up many
years ago and a few plants, mainly in Japan, are
working with insoluble anodes.

The main reactions involved in the metallic tin dis-
solution process are:

2Sn + O2 + 4H → 2Sn²+ + 2H₂O

1.

Sn + O2 + 4H* → Sn4+ + 2H₂O

PARAMETER

BENEFIT

2.

2Sn² + O2 + 4H* → 2Sn** + 2H₂O

4+

Constant tin cov-

Less tin consumed

3.

ering on strip
Better edges

Sn²+2PSA → Sn(PSA)2

4.

Better strip quality, particularly
important for thin coatings
Reduced labour costs, higher
productivity and flexibility,
safer and better working envi-
ronment

Sn+ Sn 4+ 2Sn²+

5.

No anode

handling

Oxygen is necessary to enhance the reaction rate of
the oxidation of tin by the acidity of the bath formed
at the insoluble anode.

No anode melting
plant
Covering on tanks
Electrolyte always
under control
Anodes closer to
strip

Reduced labour

The electrochemical reactions occurring at the elec-
troplating site with insoluble anodes are:

Less fumes

Lower electrolyte discharge,
consumption and pollution
Reduced electricity consump-
tion

2Sn24e2Sn (cathode)

6.

2H₂O → O2 + 4e¯ + 4H* (anode)

7.

Table 2- Advantages of insoluble-anode process

The four moles of hydrogen ions formed at the an-
ode (reaction 7) restore the as many moles of hy-
drogen ions consumed in the dissolution reactor to
dissolve two moles of metallic tin (reaction 1),
which, in turn, restore the two moles of tin depos-
ited on the strip (reaction 6). Thus the mass balance
is assured.

The process of chemical tin dissolution, using oxy-
gen to accelerate the oxidation reaction of metallic
tin to ionic tin, cannot avoid the formation of a
Sn(IV)-based sludge.

The critical point of the process is the high produc-
tion of sludge in the present tin dissolution systems
used in the electrotinning lines with insoluble an-
odes.

PILOT LABORATORY LINE

The tin lost in sludge is higher than 10% of the dis-
solved tin. This is the reason why the tinplate proc-
ess with insoluble anodes is not yet used worldwide.
Techint, in cooperation with CSM, developed an in-
novative process for dissolving tin.

After a first set of laboratory investigations, a 30 1
capacity pilot reactor for tin dissolution was initially
realised at CSM laboratories (figure 1).

The plant comprises a tin dissolution section and a
tin electroplating section. The dissolution section
contains the chemical reactor, the pressurizing
pump, the oxygen feeder and the tank for the prepa-
ration and storage of the solution.

This process is able to minimize the amount of
sludge and loss of Sn and has been successfully
proven through extensive tests on Siderar's tinning
line.

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Electrolytic solution flow rate

Tin particle size

An additional test was performed at high tempera-
ture (~60°C) to evaluate the influence of this pa-
rameter on the dissolution kinetics and sludge for-
mation.

The effect of the above parameters on the tin disso-
lution rate and on the sludge production allowed for
the definition of the criteria for designing an indus-
trial tin dissolution plant able to generate a low
amount of sludge.

PILOT PLANT CONNECTED TO AN INDUS-
TRIAL LINE

Figure 1 – CSM pilot plant

-

In a further phase of the work an industrial-scale re-
actor was realised to feed one insoluble anodes elec-
trolytic cell of the electro tinning line of Siderar
Works in S. Nicolas, Argentina (figure 2).

The PSA electrolyte flows through the reactor by
means of a pump operating at a pressure of up to 8
bar. Oxygen is fed into the depleted electrolyte by a
special feeder designed to minimize the size of oxy-
gen bubbles and promote their immediate dissolu-
tion. The electroplating section has a vertical elec-
trolytic cell with flat parallel electrodes, a pump for
solution movement and a recirculation tank.

Since the tin dissolution rate is proportional to oxy-
gen activity, oxygen-saturated electrolyte at pres-
sures higher than 1 bar, are used. A nozzle for feed-
ing oxygen into the solution was specifically devel-
oped for this purpose.

The dissolution of metallic tin achieved through
oxidation in acidic environment by dissolved oxy-
gen involves two main technological problems: i) to
get the maximum solution of gaseous oxygen, pos-
sibly up to its saturation, even when working under
pressure, ii) to maximize the mass transport coeffi-
cient using a fluidized bed reactor, which also
minimizes the non-reactive volume of the tin
charge.

A

Preliminary pilot tests

A first series of tests were carried out by varying the
following parameters:

Oxygen flow rate

Height of the fluidized tin bed

Figure 2 - Tin Dissolving Pilot Plant at Siderar

Surface area of metallic tin

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Techint Technologies decided to design the pre-
wetting tank so that it could be used either as a
normal pre-wetting tank or as an insoluble anode
plating tank connected to a dedicated tin dissolution
plant for replenishing the plated-out tin.

depending on the tin dissolution rate set in the plant,
and the call for charging is performed by the plant
automatic system when the quantity inside the reac-
tor has reached a minimum value.

The reactor is a vertical cylindrical vessel, divided
in two parts: the upper part has a large diameter to
avoid small tin particles to escape from the reactor.
The total volume is about 1 m³.

The tin dissolution plant was erected, connected to
the revamped line and began operation at the begin-
ning of 2001. By the end of the same year the re-
search activity connected to this first industrial
campaign was completed.

The plating solution is fed from the bottom into the
reactor through a distributor that supports the metal-
lic tin particles and distributes the solution. Before
entering the reactor the solution is enriched in dis-
solved oxygen.

The schematic flow diagram of the plant is here be-
low shown in figure 3.

Suitable heat exchangers are installed in the circuits
in order to maintain the plating solution at a con-
stant temperature and, because of the drag-out from
the plating tanks in order to keep the level constant
in the two recirculating tanks, a refilling of solution
from the normal line is available. The plating tank is
equipped with insoluble anodes located in the tank
as shown in figure 4.

SKETCH OF THE INDUSTRIAL PILOT PLANT at SIDERAR WORK

FLOOR LEVEL

2nd Step
1st Plating Tank

1st Step
Pre-Wetting

TK 1-7 MC

REACTOR
CIRCUIT

FILTER

BASEMENT

PLATING
CIRCUIT

TK 2-3 MC

FILTER
CIRCUIT

Figure 3 – Scheme of the industrial-scale reactor

The plant consists of a reactor into which irregular
sized tin pellets of about 2 mm diameter, are
charged into the metallic tin bed from the top of the
reactor, four recirculating circuits and two recircu-
lating tanks, one of which was already existing in
the old line.

The first circuit feeds the plating tank from which
the low tin ion content solution is returned because
of the deposition of tin on the running strip; and a
second circuit connects the two recirculation tanks.
A third, and most import circuit, feeds the tin disso-
lution reactor. This circuit works at high pressure
(5-6 bar) in order to provide high solubility of oxy-
gen in the solution. The fourth circuit removes the
sludge from the solution. The tin dissolution plant
has a design capacity of 30 kg/h of dissolved tin.
The charging system was designed with proper
automatic valves to maintain the recirculation inside
the reactor during the charging operation. The tin is
charged in the reactor once every two to three hours

Figure 4 - Insoluble anodes in industrial plant

The Iridium Mixed Metal Oxide covered titanium
anodes are connected to two rectifiers each having a
capacity of 4,000 A. The replenishing rate of the
plant is controlled by the flow rate of the oxygen.
The plant can work in three modes:

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The results were very good (see figure 5); the plant
was able to reach a dissolution rate higher than 40
kg/h without loss in efficiency and without higher
generation of sludge.

at constant oxygen flow rate (manual)
at constant tin dissolution rate (auto 1 mode)

at a rate proportional to the current given by the
rectifiers (auto 2 mode).

In the Autumn campaign the sludge percentage was
very low with a maximum rate of 4%, expressed as
tin lost in sludge vs. dissolved tin; the only excep-
tion being in the fifth test when the plant was set
outside the standard conditions for a final check.

This last mode permits working at constant tin con-
centration in the solution because the replenishing
rate is calculated taking into consideration the tin
plated out at any given moment.

A simulation model was developed to providing a
continuous on-line calculated value of actual disso-
lution rate, based on the following main process pa-
rameters: the tin charge, pressure, temperature, in-
jected oxygen and recirculating solution flow rate.

% OF TIN LOST IN SLUDGE
RESULTS FROM PLANT OPERATION

Techint Results

15%
14%

12-13 %: Actual average from competitors

13%
12%

10%: Actual minimum from competitors

11%

10%

9%
8%

INDUSTRIAL TIN DISSOLUTION
AND DEPOSITION TESTS

FIRST

5%: Declared minimum from competitors

7%

6%

5%

I

4%

3%
2%

Continuous weekly tests with simultaneous dissolu-
tion and tin-plating were performed. No problems
were encountered with the line operation or product
quality and during the test operation the plant
mainly worked at constant tin dissolution rate for
calibration purposes.

1%

0%

S3

A3 A4
AUTUMN CAMPAIGN

S1

S2

S4
SUMMER CAMPAIGN

S5

S6

A1

A2

A5

A6

Figure 5 – Tin losses during summer and autumn
campaigns

The dissolution rate was found to always depend on
the oxygen flow rate while working in conditions of
full solubility of oxygen according to Henry's law.
This was demonstrated at reactor pressures of 2, 3
and 4 bar.

During the autumn tests, tinplate with a coating
weight of 2 g/m² for each side was produced us-
ing only the first electrolytic cell equipped with in-
soluble anodes and fed with the electrolyte coming
from the tin dissolution reactor.

At each test the quantity of generated sludge was
weighed and correlated with the dissolved tin. The
sludge can be generated both in the dissolution and
plating circuits. The weighed amount is the total
from the two circuits.

Then, tinplate with the same tin weight was pro-
duced, for comparison, using only the second elec-
trolytic cell, equipped with soluble anodes and fed
with classic electrolyte coming from the storage
tanks.

Depending on the operating conditions (pressure,
injection of oxygen, tin charge, solution flow rates,
and so on) different quantities of tin lost in the
sludge were measured.

No difference was seen as far the visual appearance
of the two products. SEM (Scanning Electron Mi-
croscope) and GDOES (Glow Discharge Optical
Emission Spectroscopy) investigations (figures 6-9)
confirmed that the tinplate produced with insoluble
anodes is quite equal to that produced with soluble
anodes.

Two main test campaigns were performed (in sum-
mer and in autumn). In the first one, performed dur-
ing summer 2001, the behavior of the plant was
tested in different operating conditions by varying
one parameter at a time and keeping the others con-

stant.

Then the plant was set up in the best operating con-
dition working out from the results of the first cam-
paign. A second industrial campaign was carried out
in the autumn 2001.

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Tinplate produced with insoluble anodes

100%

90%

Concentration (weight %)

80%

70%

Iron
Tin

60%

50%

Chromium
Oxygen

40%

30%

20%

10%

0%

0 50 100 150 200 250 300 350 400 450 500
Thickness (nm)

MAR

Figure 9 - Element profile, tinplate insoluble anodes

100μm
X100 21 mm

00006 20KV

Figure 6 – Tinplate produced with soluble anodes

PILOT TESTS WITH DIFFERENT ELEC-
TROLYTES

1B

All the activities and the results described above
were performed with PSA-based electrolyte
containing Diphone V as additive.

To test the low-sludge tin-dissolution process also
with baths having different additives (Diphone VI,
ENSA) and with new ecological baths based on
MSA system, a new series of tests was carried out
on the pilot dissolution plant at CSM laboratories.
The trials were carried out at different dissolution
rates and with different electrolytes, monitoring the
total amount of generated sludge, the consumptions
of the additives and the quality of tinplate by the
Hull cell test.

100μm

00006 20KV

X100 21mm

Figure 7 - Tinplate produced with insoluble anodes

Four types of electrolytes were used in the tests:

PSA + Diphone 5
PSA + Diphone 6

-

PSA ENSA 6

Tinplate produced with soluble anodes

Ronastan system (MSA + proprietary addi-
tives)

100%
90%

Concentration (weight %)

80%
70%
60%

The electrolyte volume was 500 1. The tests were
made with a flow rate of 5 m³/h and a pressure of 5

Iron
Tin

50%

ata.

Chromium
Oxygen

40%

Also electrolytes containing up to 15 g/l Fe were
tested to check the effect of such ion on the loss of
tin in sludge. Fe ion is generally present in tin
electrolyte owing to the dissolution of steel strip in
the first half cell (pre-dip).

30%

20%
10%-

++

0%

400

200

500

300
Thickness (nm)

0

100

Figure 8 – Element profile, tinplate soluble anodes

The results were really good with all the electro-
lytes. Very low percentages of tin loss were de-

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rate, according to the current applied in the two
electrolytic cells equipped with insoluble anodes.

tected, with a maximum rate of 4,5 %, no matter the
electrolyte used (figure 6).

Thus, the amount of tin dissolved at any time is
equal to that of tin deposited on the strip, plus the
amount of tin to compensate the drag-out.

Tin lost in sludge

5,0

4,5

ווווי
PSA+Diphone 6

Tin in sludge vs. tin dissolved (%)

0,0

PSA+Diphone 5

PSA+ENSA 6

MSA+SG+TP

PSA+Diphone 5

Figure 6 – Tin loss with various electrolytes

As low percentage of tin loss were found even with
the same electrolytes containing up to 15 g/l iron
(figure 7).

Figure 8
paign.

Insoluble Anodes in 2004 industrial cam-

-

Two long-term running tests were carried out. The
amount of sludge was measured at the end of each
test and correlated to the dissolved tin. The total
amount of tin lost resulted less than 4 %.

Tin lost in sludge

5,0
4,5
4,0
3,5
3,0
CNN w w A A S

Tin in sludge vs. tin dissolved (%)

13,5gl Fe

The insoluble anodes were connected to four rectifi-
ers for a total capacity of 22,000 A. Figure 9 shows
the amount of current provided, during normal op-
erating conditions of the line, with insoluble anodes,
which is proportional to the tin plated with insoluble
anodes. In general more than 30 % is given with in-
soluble anodes, up to a maximum of 45 % in case of
low coating (2.2 g/m²).

15,1 gl Fe

12,7 gl Fe

4,5g/l Fe

0,5

0,0

PSA+Diphone 6

PSA+ENSA 6

PSA+ENSA 6

MSA+SG+TP

Two commercial coils were also produced only with
insoluble anodes.

Figure 7 – Tin loss with electrolytes containing Fe

Figure 10 shows the progressive amount of tin dis-
solved and plated out during one test.

SECOND INDUSTRIAL TIN DISSOLUTION
AND DEPOSITION TESTS

The very good results obtained in the previous in-
dustrial campaign with only the pre-dip cell
equipped with insoluble anodes, were confirmed
even in this second campaign with one cell and a
half equipped with insoluble anodes.

In May and June 2004 a second industrial campaign
was carried out at Siderar electrotinning line. Both
the pre-dip half cell and the second electroplating
cell were equipped with insoluble anodes.

An automatic procedure was adopted to set the oxy-
gen flow rate and, consequently, the tin dissolution

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TECHINT

95% Operating time with
INSOLUBLE ANODES
525.5 tons with INS. ANODES

Tin plated with insoluble anodes / Total Tin deposit
on 18/5/04 (8° day)

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

Tin coating g/m²

0%

* 3 3 5 3 3 3 3 3 3 3 3

23.28

Time [h.min]

Fig. 9 - Amount of current given with Insoluble Anodes during one typical day

CONCLUSIONS

Last trials carried out on a pilot laboratory plant at
CSM showed that the process is insensitive to the
type of tinplating electrolyte. In fact, there were no
significant differences between the amounts of
sludge generated with phenol-sulphonic acid (PSA)
either with addition of DIPHONE or ENSA, and
methanesulphonic acid (MSA). Moreover also the
presence of Fe ions in solutions has been checked.
The results showed no influence on the amount of
produced sludge.

TIN DISSOLVED AND TIN PLATED OUT

3500.0

3000.0

DISS.
PLATED

2500.0

2000.0

kg

1500.0

1000.0

500.0

0.0

11/05/2004 12/05/2004 13/05/2004 14/05/2004 15/05/2004 16/05/2004 17/05/2004 18/05/2004

The second industrial campaign confirmed that the
Techint-CSM tin dissolution process is able to pro-
duce a tin loss in sludge as great as that of the clas-
sic electrotinning process based on the use of solu-
ble anodes.

Day

Figure 10 – Tin dissolved and plated out during a test

Thanks to such results, the tinplate process with in-
soluble anodes is ready for full industrialisation,
bringing all the advantages connected to the use of
insoluble anodes, which were not exploited so far
for the absence of a low sludge dissolution system.
A further step in the direction of a full insoluble an-
odes line is scheduled for the tinning line at Siderar
work, where a third plating tank is going to be
equipped with insoluble anodes.

Electrolytic El tinplate was produced by using only
the two cells with insoluble anodes. No visual dif-
ference in the aspect was seen in comparison to El
tinplate produced with soluble anodes. Samples of
such tinplates are under investigation by SEM and
GDOES techniques.

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TECHINT

REFERENCES

1. J. Lampereur et al.; “Electrotinning at high cur-
rent densities"; Proceedings 4th International
Tinplate Conference, (1988)
2. B. Paramanathan, E. N. Soepenberg; "A pilot
plant for steel strip coating by radial jet elec-
trolysis at high current densities", ECSC Final
Report EUR 17817 EN, (1997)
3. B. Colinel; “Electrolyte and apparatus for elec-
troplating at high current density"; Proceedings
6th International Tinplate Conference, (1996)

Y. Suganuma et al.; Method for electrolytic tin
plating of steel plate"; U.S. Patent No.
5194141, (1993)

4.

B. Paramanathan, “Method and apparatus for
the electrolytic coating of one side of a moving
metal strip"; EP No. 0 364 013 B1, (1994)
6. M. Kitayama et al.; «Process for electro-tin
plating » ; U.S. Patent No. 4181580, (1980)
H. Bunk et al.; "Method of electrolytic tinning
using an insoluble anode"; EP No. 0 268 823
B1, (1987)

5.

7.

D. L. De Respiris et al.; “Process for replenish-
ing metals in aqueous electrolyte solutions";
U.S. Patent No. 5082538, (1992)
T. Kikuchi et al.; "Tinning apparatus and tin-
ning method"; JP No. 8-20889, (1996)

8.

9.

10. D. Thomson; “Electrolytic tin plating method";
U.S. Patent No. 5312539, (1994).

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The tin lost in sludge is higher than 10% of the dissolved tin. This is the reason why the tinplate process with insoluble anodes is not yet used worldwide.