Sulphuric acid is a cyclical
commodity. Production of this intermediate product, consumed by
myriad markets in the manufacture of high value goods, is often
cited as being the best indication of a countrys
industrial wealth and activity.
This is because production of
sulphur-in-all-forms (including sulphuric acid) is primarily
driven by demand for base metals and hydrocarbons, as the
manufacture of these commodities also produces sulphur
Involuntary production of any
commodity essentially means that its availability is not fully
driven by its own consuming markets. In the case of sulphuric
acid, its availability is prone to erratic swings in oversupply
and undersupply (in addition to eye-watering price cycles)
depending on the ratio between production and
The sulphuric acid market has seen tremendous turnaround in the
past two years. Perhaps most illustrative of the scale of
market change has been the sulphur spot price: in 2008 sulphur
was being purchased for an astonishing $800/tonne but by
2009 prices actually became negative.
Sulphuric acid is the most widely
used inorganic chemical with end markets including fertilisers,
metal production (principally copper), petroleum, rubber, and
pulp and paper.
It is also an essential component
for processing a range of industrial minerals to yield vital
prerequisite chemical products, eg. phosphate rock to
phosphoric acid, borates to boric acid, fluorspar to
hydrofluoric acid, lithium carbonate to lithium sulphate and
ilmenite to titanium dioxide (see panel).
Although its applications are
numerous, 65% of the chemical is used in various forms for
agricultural purposes (Figure 1). Thus sulphuric acid
is heavily dependent on the fortunes of the fertiliser industry
Ð particularly phosphate.
The fertiliser mine to market chain
has been hit hard in the past 18 months. As government focus
leaped from food security to the fallout of the banking crisis,
fertilisers and their raw materials became of secondary
importance (IM March 10, p.48: Forgotten
Likewise production of other
high-value commodities Ð such as copper and petroleum Ð
was scaled back as demand evaporated.
2009 saw markets quite
depressed after the highs of 2007/8 and the subsequent price
crash, Richard Hands, editor of Sulphur, told
IM: However, China has been importing
sulphur and sulphuric acid quite heavily through the last half
of 2009, and this is starting to send prices climbing
This is good news for the industry,
particularly for sulphuric acid producers who manufacture the
chemical involuntarily ie. through the metal smelting
process Ð as they need to sell sulphuric acid simply to
clear their storage areas.
Around 205-207m. tonnes of
sulphuric acid were produced in 2008. Of this, approximately
60m. tonnes were produced involuntarily principally as
smelter acid from metal production (Figure 2).
In periods of oversupply or low
prices, smelter acid poses a nuisance to metal producers. When
sulphuric acid prices became negative in 2008, these producers
were actually forced to pay consumers to take away
their unwanted stock.
But now demand is returning, and
with it availability is tightening. Hands explained: A
lot of mining operations virtually shut down at the start of
the crash, but are back into production again. Farmers stopped
buying phosphate fertiliser when prices were sky-high but are
now back in the market, so fertiliser producers are running at
higher operation rates.
Around 65% of total sulphuric acid
production is used for agriculture, with phosphoric acid
production being the primary component of this (Figure
3). Sulphuric acid is used to convert phosphate rock to
phosphoric acid which itself is used in the production of
phosphate fertilisers, such as diammonium phosphate.
In this process, phosphate rock is
acidulated using sulphuric acid. The sulphuric acid reacts with
calcium in the phosphate rock, forming gypsum. As gypsum is not
removed from superphosphate, around 12% of the fertiliser
comprises sulphur. Sulphur can also be removed to produce a
higher nutrient phosphate-based fertiliser.
Some sulphur-based fertilisers such
as ammonium sulphate use sulphuric acid in their
manufacture. Ammonium nitrate-sulphate is also made by
granulating ammonium sulphate with ammonium nitrate or
neutralising sulphuric acid with ammonia in ammonium nitrate
Moreover, sulphur is an important
plant nutrient in its own right. Richard Hands told
IM: The move towards higher analysis
fertilisers, such as urea and diammonium phosphate, and away
from more traditional sulphur-containing fertilisers, such as
ammonium sulphate and triple superphosphate, has led to sulphur
deficiencies in many soils, especially in Asia.
Cleaning up of stack gas emissions
from power stations to reduce sulphur dioxide in the atmosphere
(and thus acid rain) has also meant that there is less free
sulphur in soils. The Sulphur Institute (TSI) believes that
there is a sulphur gap in terms of plant nutrient that
may be tens of millions of tonnes worldwide.
India has recently recognised
this [gap] and will now be subsidising fertiliser use in terms
of nutrient content, including sulphur, Hands revealed.
This has the potential to increase demand for
sulphur-containing fertilisers, which may include those using
Yet TSI forecasts traditional
sulphur fertiliser products will not meet the increasing demand
for sulphur in agriculture. TSI estimates that sulphur
fertilisers provide a potential market of 9.6m. tpa sulphur
Copper is produced through the
solvent extraction-electro-winning (SX-EW) process, whereby
metals from the host rock are dissolved in sulphuric acid.
Another important market is nickel production, which uses
sulphuric acid in the pressure acid leach process. Around 30
tonnes of sulphuric acid are needed for each tonne of nickel
In total, base metals represent
about 10% of acid demand. Moreover, leaching treatment of metal
ores is a rapidly growing area for sulphuric acid; particularly
in nickel production. New technologies like high pressure
acid leaching have the potential to transform the nickel
industry, Hands commented.
But metal markets themselves are
also cyclical and production of commodities such as copper and
steel has varied enormously over the past 18 months.
For example, copper for delivery in
three months traded as high as $7,660/tonne at the London Metal
Exchange on 6 January 2010, compared with $2,845/tonne on 24
Prices are well above the
cost of production to the point that the CEO of
Antofagasta, Marcelo Awad, said this month that as a producer
he believed the market would be more sustainable at much lower
levels of between around $5,000-5,500/tonne, Alex
Harrison, non-ferrous editor of Metal Bulletin, told
Copper prices have climbed strongly
since being battered down to levels below $3,000/tonne in the
wake of the global financial crisis on a potent combination:
continuing growth in China, the worlds largest copper
buyer, and investors move into commodities as an asset
class, Harrison explained.
But what does this mean for
sulphuric acid? Aker Solutions, a leading provider of
engineering and construction services, told IM
that leaching markets had continued to increase, although the
sulphuric acid market as a whole was improving, but still
Meanwhile Bob Braun, president of
USA-based sulphuric acid pump manufacturer Chas S. Lewis &
Co. Inc., revealed: Smelting markets are coming around
slowly but there are still some issues with the commodity
prices being depressed.
For the moment the sulphuric
acid market is going to stay fairly similar to the past few
years. In my opinion the market is actually at the bottom of
what it has been, Braun told IM.
We hope to see some rebound towards the end of the year
as the commodity pricing comes back and hopefully more
Sulphuric acid is one of the
primary chemicals used in the paper pulping process. Pulp is
made by mechanically or chemically separating the fibres in
wood or other cellulose materials from non-fibrous
For the pulp and paper sector, 2009
was marked by a severe global recession. UPM-Kymmene, one of
the worlds leading pulp and paper producers, suffered a
sales fall of 18% to Û7.7bn. ($10.6bn.), which the
company said had severely impacted the
profitability of its operations.
In 2010, the operating
environment will continue to be challenging, UPMs
president Jussi Pesonen acknowledged. Demand recovery
seems to be at hand, but the speed and strength of it is
uncertain. There is still overcapacity in many of our
Another suffering, high-value
market for sulphuric acid is in the production of the white
pigment titanium dioxide (TiO2). The worlds
titanium dioxide capacity is 5.625m. tpa: of this, 45% is
produced through the older sulphate route and 55% through the
In the sulphate production route,
lower grade ilmenite and titanium slag are used as feedstock.
The feedstock is added to sulphuric acid, dissolved in cold
water, and then filtered to remove ferrous sulphate. Once
filtered the material is steam-heated to precipitate
TiO2 and the solids are calcined to produce
TiO2 pigment (TiO2 93-96% - see
The sulphate route is slowly being
phased out, however, as it is less efficient than the chloride
Paul Anselme, manager of the
European Chemical Industry Council (CEFIC), told
IM: Sulphuric acid is used for acid
digestion of the mineral ores or slags containing titanium. In
this process, H2SO4 cannot be
The sulphate process uses a simpler
technology and can use lower grades and/or cheaper ores than
those used by the chloride process. Yet the sulphate process
has higher production costs and produces lower TiO2
For TiO2 producers, the
switch to the chloride route or more often the decision to
close sulphate plants is triggered by environmental and
production cost considerations.
In Europe, sulphate plants are
generally older and the trend is for companies to invest in
extension of chloride plants rather than the renovation of old
sulphate facilities, Anselme revealed.
If savings have to be made,
companies first look at sulphate plants, he said.
The closure of sulphate plants has
been seen in Europe and elsewhere following the onset of the
global recession. As with any commodity, pigment demand is
dependent on its end markets principally auto,
construction, paint and paper all of which suffered from
reduced sales last year.
Huntsman Corp.s decision to
mothball its 40,000 tpa sulphate plant in Grimsby, UK, was
blamed on decreased demand for pigments during the downturn.
The closure, in January 2009, was part of Huntsmans
worldwide cost-cutting initiative that included the loss of
1,175 jobs (IM March 09, p.19: Huntsman shuts UK
Also closed was Cristal
Globals 65,000 tpa sulphate facility in Le Havre, France.
Ultimately, high operating costs including energy and raw
material prices were given as the rationale behind the
shutdown, although Cristals chloride facility in
Baltimore, USA, suffered the same fate (IM July 09,
p.29: TiO2s time to transform).
Table 2: US sulphuric acid consumption, by use (2007)
|Pulp and paper
|Rubber & plastics (synthetic & organic)
|Other ores (uranium, vanadium)
|Other primary metals
|Exported sulphuric acid
Some sources estimate that the
sulphuric acid market is in oversupply at present, while others
believe that recessionary conditions have capped production of
the chemical particularly involuntary production from
Whichever scenario is more
accurate, it is fair to say that the future health of the
sulphuric acid market will be tied to the performance of
fertiliser, hydrocarbon and base metal markets.
Generally speaking, fertiliser is
not a necessity for crops it is merely an enhancer. Although
this is true on one level, it does not take into account the
deficit of sulphur in soils at present. Considering the sulphur
gap, fertiliser could become an ever bigger market for
sulphuric acid particularly within the next few years.
For titanium dioxide markets the
picture is less clear. While it is undeniable that producers
are slowly changing to the chloride production route,
manufacturing TiO2 through the sulphate process
enables the use of lower grade ores.
Trickier still is base metal
demand. With the gradual switch to acid leaching (a consumer of
sulphuric acid) over smelting (a producer) this market may
start to produce less and consume more sulphuric acid.
Also likely to shake-up traditional
supply chains is increased vertical integration of
Most large nickel and other
metal leaching projects have associated sulphur-burning
sulphuric acid plants, Hands told IM.
As burning sulphur is exothermic, it can also produce
electricity for the plant and even export some to local homes.
The volatility of the open acid market is also a source of
concern for consumers.
Increasingly, leaching projects are
choosing to build their own sulphur burning plants because the
sulphur market tends to be less volatile than the sulphuric
But this must be considered against
the backdrop of the global copper markets.
The move by investors into
commodities, such as copper, as an asset class is based in part
on forecasts about the continuing growth of China but also on
strategies that involve holding contracts in industrial metals,
rather than faltering paper currencies.
In the event of a double-dip
recession in the West, the bursting of an asset bubble or
tightening credit in China, copper prices are vulnerable,
Otherwise many believe that there is a long-term input in
the copper market: when prices fall to a certain level, there
will be buying interest from a confident, expansive and
Sulphuric acid at a glance
Formula: sulphuric acid, H2SO4,
is an inorganic mineral acid.
Properties: soluble in water at all
concentrations, sulphuric acid is the most widely used
World production in 2008: between 205-207m.
tonnes. Of this, around 60m. tonnes was produced involuntarily
(ie. by metal smelters).
Main producers: production of
sulphur-in-all-forms (including sulphuric acid) is primarily
driven by demand for base metals and hydrocarbons, as producers
of these commodities also produce sulphur-in-all-forms
involuntarily (Table 1).
Markets: agriculture, hydrocarbon refining,
base metal leaching, titanium dioxide pigments Ð plus
numerous other smaller markets including rubber production and
Industrial minerals: numerous industrial
minerals use sulphuric acid as an essential input for
processing. Sulphuric acid is used with phosphate rock
(phosphoric acid); potash (potassium sulphate); aluminium
trihydrate (aluminium sulphate); antimony oxide (antimony
sulphate); calcium bentonite (activated bentonite); beryllium
hydroxide (beryllium sulphate); borates (boric acid); acid
grade fluorspar (hydrofluoric acid); lithium carbonate (lithium
sulphate); magnesium hydroxide (magnesium bisulphate);
manganese carbonate (manganese sulphate); rare earths such as
bastnasite (cerium concentrate); strontium carbonate (strontium
sulphate); and ilmenite or titanium slag (titanium
Prices: at present prices for sulphuric
acid have been quoted at $120-130/tonne (Chilean landed), while
Chinese prices are in the range of $60-70/tonne. Higher sulphur
prices are forecast to push up sulphuric acid prices in the
short-term, but this is not expected to persist.
Table 1: World sulphur production, by process
||2007 (000s tpa)
||Coal, lignite, gasification
||Metallurgy (ie. copper)
||Natural gas, petroleum, tar sands,
Source: US Geological Survey
Production routes for
Table 3: Primary
sulphuric acid markets
||Sulphuric acid properties
||Sulphuric acid is used to convert phosphate rock to
phosphoric acid used as a fertiliser as
well as in the production of other fertiliser chemicals.
Around 65% of all sulphuric acid is used for
||In this process, phosphate rock is acidulated using
sulphuric acid to produce phosphoric acid. The sulphuric
acid reacts with calcium in the phosphate rock, forming
gypsum. Gypsum is not removed from superphosphate,
leaving around 12% sulphur content in the
||In some phosphate-based fertilisers the sulphur is
removed. In this process phosphate is acidulated then
further processed to manufacture a higher nutrient
phosphate-based fertiliser. In its own right sulphur is
also an important nutrient for the fertiliser
|Copper ore leaching
||Copper is produced through the solvent
extraction-electro-winning (SX-EW) process, whereby
metals from the host rock are dissolved in sulphuric
||Other non-ferrous metals are extracted using
sulphuric acid, including nickel which can be
produced using the pressure acid leach process. 30 tonnes
of sulphuric acid are needed per tonne of nickel
||Fuel refineries consume sulphuric acid in the
alkylation process to produce higher quality fuels. For
example, in petroleum refining sulphuric acid is the
catalyst for the reaction of isobutane with isobutylene
to give isooctane, a compound that raises the octane
rating of gasoline.
||This process is also the largest source of recovered
(or by-product) sulphur in the world. Although it can be
replaced by hydrochloric acid in this market, sulphuric
acid is seen as a safer product.
|Pulp and paper processing
||Pulp is made by mechanically or chemically (ie. using
sulphuric acid) separating the fibres in wood or other
cellulose materials from non-fibrous materials.
||Another important use for sulphuric acid is for the
manufacture of aluminium sulphate, used to improve the
surface of paper.
||There are two methods for producing titanium dioxide
(TiO2) pigment: the chloride route and the sulphate
route. In the sulphate production route, lower grade
ilmenite and titanium slag are used as feedstock. The
feedstock is added to sulphuric acid, dissolved in cold
water, and then filtered to remove ferrous sulphate. Once
filtered the material is steam heated to precipitate
TiO2, and the solids are calcined to produce TiO2
pigment. In this application there is no substitute for
|Inorganic chemicals & industrial minerals
||Sulphuric acid is used in numerous chemicals,
including the production of hydrofluoric acid and
aluminium fluoride; the latter of which is an important
flux chemical used in the aluminium manufacturing
||In addition the chemical is an important processing
input during the refining of numerous industrial
minerals, including borates (boric acid), fluorspar
(hydrofluoric acid), lithium carbonate (lithium sulphate)
and ilmenite or titanium slag (titanium dioxide).
||Via sulphonic acid, sulphuric acid is used as a
chemical peptizer, or processing aid, in the production
of rubber. It helps to reduce the energy needed to
produce rubber by plasticising, or lowering, the
||Peptizers are generally added at 1-3 parts phr (by
weight per hundred rubber). They reduce the molecular
weight of the compounds by increasing the rate of
oxidative chain scission.
||Sulphuric acid is used to manufacture aluminium
sulphate, a chemical used to filter impurities and
improve the taste of water.
||Lead-acid batteries store energy using a reversible
chemical reaction between different lead plates and the
electrolyte (dilute sulphuric acid).
||In the reaction, lead dioxide plates react with
sulphuric acid to form lead sulphate and a positive
charge on the plates. Meanwhile lead plates react with
sulphate ions to form lead sulphate and also become
||The passage of electrons from the lead oxide plates
to the pure lead plates is the current of electricity
generated by the cell. When the battery is recharged lead
sulphate is broken down. As a result lead dioxide is
re-deposited on the positive electrode while lead is
replaced on the negative electrode.