Carbonatation is a chemical reaction where
calcium hydroxideCalcium hydroxide, traditionally called slaked lime, hydrated lime, slack lime, or pickling lime, is a chemical compound with the chemical formula Ca2. It is a colourless crystal or white powder, and is obtained when calcium oxide is mixed, or "slaked" with water...
reacts with
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
and forms insoluble
calcium carbonateCalcium carbonate is a chemical compound with the chemical formula CaCO
3. It is a common substance found in rock in all parts of the world, and is the main component of shells of marine organisms, snails, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural...
:
- Ca(OH)2 + CO2 → CaCO3 + H2O
The process of forming a carbonate is also referred to as
carbonation, although this term can also refer to the process of
dissolving carbon dioxide in waterCarbonation occurs when carbon dioxide is dissolved in water or an aqueous solution. This process yields the "fizz" to carbonated water, sparkling mineral water, and soft drinks; the head to beer; and the cork pop and bubbles to champagne and sparkling wine.-Effervescence:Effervescence is the...
.
Carbonatation is a slow process that occurs in
concreteConcrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate , water, and chemical admixtures...
where lime (calcium hydroxide) in the
cementIn the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed...
reacts with carbon dioxide from the air and forms calcium carbonate.
Carbonatation is a chemical reaction where
calcium hydroxideCalcium hydroxide, traditionally called slaked lime, hydrated lime, slack lime, or pickling lime, is a chemical compound with the chemical formula Ca2. It is a colourless crystal or white powder, and is obtained when calcium oxide is mixed, or "slaked" with water...
reacts with
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
and forms insoluble
calcium carbonateCalcium carbonate is a chemical compound with the chemical formula CaCO
3. It is a common substance found in rock in all parts of the world, and is the main component of shells of marine organisms, snails, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural...
:
- Ca(OH)2 + CO2 → CaCO3 + H2O
The process of forming a carbonate is also referred to as
carbonation, although this term can also refer to the process of
dissolving carbon dioxide in waterCarbonation occurs when carbon dioxide is dissolved in water or an aqueous solution. This process yields the "fizz" to carbonated water, sparkling mineral water, and soft drinks; the head to beer; and the cork pop and bubbles to champagne and sparkling wine.-Effervescence:Effervescence is the...
.
Concrete
Carbonatation is a slow process that occurs in
concreteConcrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate , water, and chemical admixtures...
where lime (calcium hydroxide) in the
cementIn the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed...
reacts with carbon dioxide from the air and forms calcium carbonate. Since carbonatation causes a lower
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
(
acidAn acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0...
ic), this may lead to
corrosionCorrosion is the disintegration of a material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a...
of the
steel reinforcing rodsA rebar, or reinforcing bar, is a common steel bar, and is commonly used in reinforced concrete and reinforced masonry structures. It is usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete. It can also be described as reinforcement or reinforcing...
and damage to the construction.
Sugar refining
The carbonatation process is used in the production of
sugarSugar is a class of edible crystalline substances, mainly sucrose, lactose, and fructose. Human taste buds interpret its flavor as sweet. Sugar as a basic food carbohydrate primarily comes from sugar cane and from sugar beet, but also appears in fruit, honey, sorghum, sugar maple , and in many...
from
sugar beetSugar beet , a member of the Chenopodiaceae family, is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar production....
s.
It involves the introduction of milk of lime (calcium hydroxide
suspensionIn chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometre. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...
) and carbon dioxide enriched gas into the "raw juice" (the sugar rich liquid prepared from the diffusion stage of the process) to form calcium carbonate and precipitate impurities that are then removed. The whole process takes place in "carbonatation tanks" and processing time varies from 20 minutes to an hour.
Carbonatation involves the following effects:
- The increase in alkalinity
Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. Alkalinity is closely related to the acid neutralizing capacity of a solution and ANC is often incorrectly used to refer to alkalinity.The alkalinity is...
coagulatesCoagulation is a complex process by which blood forms clots. It is an important part of hemostasis , wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
s in the juice.
- Calcium carbonate absorbs colourants
- Alkalinity destroys some monosaccharide
Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose and ribose...
sugars, mostly glucoseGlucose , a monosaccharide also known as - grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate...
and fructoseFructose is a simple monosaccharide found in many foods. It is a white solid that dissolves readily in water. Honey, tree fruits, berries, melons, and some root vegetables, contain significant amounts of the fructose derivative sucrose...
The target is a large particle that naturally settles rapidly to leave a clear juice. The juice at the end is approximately 15
°BxDegrees Brix is a measurement of the dissolved sugar-to-water mass ratio of a liquid. It is measured with a saccharimeter that measures specific gravity of a liquid or more easily with a refractometer. A 25 °Bx solution is 25% , with 25 grams of sugar per 100 grams of solution...
and 90%
sucroseSucrose, commonly called table sugar, is a moosaccharide of glucose and fructose with the molecular formula C12H22O11. This white, odorless, crystalline powder has a pleasing, sweet taste. It is best known for its role in human nutrition...
. The
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
of the thin juice produced is a balance between removing as much
calciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust...
from the solution and the expected pH drop across later processing. If the juice goes
acidAn acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0...
ic in the
crystallisationCrystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas...
stages then sucrose rapidly breaks down to
glucoseGlucose , a monosaccharide also known as - grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate...
and
fructoseFructose is a simple monosaccharide found in many foods. It is a white solid that dissolves readily in water. Honey, tree fruits, berries, melons, and some root vegetables, contain significant amounts of the fructose derivative sucrose...
; not only do glucose and fructose affect crystallisation but they are
molassagenicMolasses is a viscous byproduct of the processing of sugar cane or sugar beets into sugar. The word molasses comes from the Portuguese word melaço, which ultimately comes from mel, the Latin word for "honey". The quality of molasses depends on the maturity of the sugar cane or sugar beet, the...
taking equivalent amounts of sucrose on to the molasses stage.
The carbon dioxide bubbled through the mixture forms calcium carbonate. The non-sugar solids are incorporated into the calcium carbonate particles and removed by natural (or assisted)
sedimentationSedimentation is the tendency for particles in suspension or molecules in solution to settle out of the fluid in which they are entrained, and come to rest against a wall...
in tanks.
There are several systems of carbonatation, named from the companies that first developed them. They differ in how the lime is introduced, the temperature and duration of each stage, and the separation of the solids from the liquid.
- Dorr
Dr John Van Nostrand Dorr was an industrial chemist active in early to middle twentieth century. He attended Rutgers University, where he was admitted to the Zeta Psi fraternity, graduating in 1896...
(also Dorr-Oliver) - a continuous process using two tanks with recycling ("1st carbonatation") to build up particle size for natural flocculationFlocculation is, in the field of chemistry, a process where colloids come out of suspension in the form of floc or flakes. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution.-Term...
. The recycling ratio is about 7:1. The particles are separated under gravity in a thickening stage in a vessel called a clarifier. The clear juice is then gassed further in another tank ("2nd carbonatation") and filtered. The concentrated mud (underflow) is filtered and/or pressed to recover more liquid. The Dorr process is low in maintenance and man-power but susceptible to frost damaged beet. It is favoured in the UK and the USA.
- DDS
-Computer and information science:*Data Design System, DDS-CAD software vendor*Data Description Specifications, AS400 programming*Data Distribution Service, a OMG standard for publish/subscribe middleware for distributed systems....
(Det Danske Sukkerfabrik - "The Danish Sugarfactory") -- multistage process involving pre-liming where the pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
of the juice is gradually increased to start precipitation of proteins, followed by addition of further lime and gas. The particles are removed at each stage by filtration.
- RT
-Miscellaneous:*Real-time *Reform Treaty, of the European Union*Routing transit number - a nine digit bank code, used in the United States, which appears on the bottom of negotiable instruments such as checks that identifies which financial institution it is drawn upon-Computers:*Run time *Request...
(Raffinerie Tirlemontoise) - another multistage process with a pre-liming stage. Particles also removed by filtration.
Both DDS and RT processes are favoured by
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
an factories.
The clear juice from carbonatation is generally known as "thin juice". it may undergo pH adjustment with soda ash and addition of
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
("sulfitation") prior to the next stage which is concentration by multiple effect evaporation.
See also
- Phosphotation - a similar process used in sugarcane processing.
External links