Lead chamber process
Encyclopedia
The lead chamber process was an industrial method used to produce sulfuric acid
in large quantities. It has been largely supplanted by the contact process
.
In 1746 in Birmingham, England, John Roebuck
began producing sulfuric acid
in lead
-lined chambers, which were stronger, less expensive, and could be made much larger than the glass
containers which had been used previously. This allowed the effective industrialization of sulfuric acid production and with several refinements, this process remained the standard method of production for almost two centuries. So robust was the process that as late as 1946, the chamber process accounted for 25% of sulfuric acid manufactured.
is introduced along with steam and oxides of nitrogen
into large chambers lined with sheet lead
where the gases are sprayed down with water and chamber acid. The sulfur dioxide and nitrogen dioxide dissolve and over a period of approximately 30 minutes, the sulfur dioxide oxidized to sulfuric acid. The presence of nitrogen dioxide is necessary for the reaction to proceed. The process is highly exothermic, and a major consideration of the design of the chambers was to provide a way to dissipate the heat formed in the reactions. Early plants used very large wooden rectangular chambers (Faulding box chambers) that were cooled by ambient air. Around the turn of the nineteenth century, such plants required about half a cubic meter of volume to process the sulfur dioxide equivalent of a kilogram of burned sulfur. In the mid 19th century, French chemist Gay-Lussac
redesigned the chambers as stoneware packed masonry cylinders. In the 20th century, plants using externally cooled Mills-Packard chambers supplanted the earlier designs.
Sulfur dioxide for the process can be provided by burning elemental sulfur
or by the roasting
of sulfur containing metal ores
in a stream of air in a furnace. During the early period of manufacture, nitrogen oxide
s were produced by the decomposition of niter at high temperature in the presence of acid, but this process was gradually supplanted by the air oxidation of ammonia
to nitric oxide
in the presence of a catalyst. The recovery and reuse of oxides of nitrogen was an important economic consideration in the operation of a chamber process plant.
In the reaction chambers, nitric oxide
reacts with oxygen to produce nitrogen dioxide
. Liquor from the bottom of the chambers is diluted and pumped to the top of the chamber and sprayed downwards in a fine mist. Sulfur dioxide and nitrogen dioxide are absorbed in the liquid and react to form sulfuric acid and nitric oxide. The liberated nitric oxide is sparingly soluble in water and returns to the gas in the chamber where it reacts with oxygen in the air to reform nitrogen dioxide. Some percentage of the nitrogen oxides are sequestered in the reaction liquor as nitrosylsulfuric acid
and as nitric acid, so fresh nitric oxide must be added as the process proceeds. Later versions of chamber plants included a high temperature Glover tower to recover the nitrogen oxides from the chamber liquor, while concentrating the chamber acid to as much as 78% H2SO4. Exhaust gases from the chambers are scrubbed by passing into a tower through which some of the Glover acid flows over broken tile. Nitrogen oxides are absorbed to form nitrosylsulfuric acid which is then returned to the Glover tower to reclaim the oxides of nitrogen.
Sulfuric acid produced in the reaction chambers is limited to about 35% concentration. At higher concentrations, nitrosylsulfuric acid
precipitates on the lead walls as chamber crystals
and is no longer able to catalyze
the oxidation reactions.
or by roasting pyritic ore
in a current of air:
Nitrogen oxides are produced by decomposition of niter in the presence of sulfuric acid or hydrolysis of nitrosylsulfuric acid
:
In the reaction chambers, sulfur dioxide and nitrogen dioxide dissolve in the reaction liquor. Nitrogen dioxide is hydrated to produce nitrous acid
which then oxidizes the sulfur dioxide to sulfuric acid and nitric oxide. The reactions are not well characterized but it is known that nitrosylsulfuric acid is an intermediate in at least one pathway. The major overall reactions are:
Nitric oxide escapes from the reaction liquor and is subsequently reoxidized by molecular oxygen to nitrogen dioxide. This is the overall rate determining step in the process:
Nitrogen oxides are absorbed and regenerated in the process, and thus serve as a catalyst
for the overall reaction:
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
in large quantities. It has been largely supplanted by the contact process
Contact process
The contact process is the current method of producing sulphuric acid in the high concentrations needed for industrial processes. Platinum was formerly employed as a catalyst for the reaction, but as it is susceptible to poisoning by arsenic impurities in the sulfur feedstock, vanadium oxide is...
.
In 1746 in Birmingham, England, John Roebuck
John Roebuck
This article is about the English inventor. For the 19th century British politician, see John Arthur Roebuck.John Roebuck FRS was an English inventor who played an important role in the Industrial Revolution and who is known for developing the industrial-scale manufacture of sulfuric acid.-Life...
began producing sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
in lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
-lined chambers, which were stronger, less expensive, and could be made much larger than the glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
containers which had been used previously. This allowed the effective industrialization of sulfuric acid production and with several refinements, this process remained the standard method of production for almost two centuries. So robust was the process that as late as 1946, the chamber process accounted for 25% of sulfuric acid manufactured.
The Process
Sulfur dioxideSulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
is introduced along with steam and oxides of nitrogen
Nitrogen oxide
Nitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:* Nitric oxide, also known as nitrogen monoxide, , nitrogen oxide* Nitrogen dioxide , nitrogen oxide...
into large chambers lined with sheet lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
where the gases are sprayed down with water and chamber acid. The sulfur dioxide and nitrogen dioxide dissolve and over a period of approximately 30 minutes, the sulfur dioxide oxidized to sulfuric acid. The presence of nitrogen dioxide is necessary for the reaction to proceed. The process is highly exothermic, and a major consideration of the design of the chambers was to provide a way to dissipate the heat formed in the reactions. Early plants used very large wooden rectangular chambers (Faulding box chambers) that were cooled by ambient air. Around the turn of the nineteenth century, such plants required about half a cubic meter of volume to process the sulfur dioxide equivalent of a kilogram of burned sulfur. In the mid 19th century, French chemist Gay-Lussac
Joseph Louis Gay-Lussac
- External links :* from the American Chemical Society* from the Encyclopædia Britannica, 10th Edition * , Paris...
redesigned the chambers as stoneware packed masonry cylinders. In the 20th century, plants using externally cooled Mills-Packard chambers supplanted the earlier designs.
Sulfur dioxide for the process can be provided by burning elemental sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
or by the roasting
Roasting (metallurgy)
Roasting is a step in the processing of certain ores. More specifically, roasting is a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component. Often before roasting, the ore has already been partially purified, e.g. by froth...
of sulfur containing metal ores
Sulfide mineral
The sulfide minerals are a class of minerals containing sulfide as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, the arsenides, the antimonides, the bismuthinides, the sulfarsenides and the sulfosalts...
in a stream of air in a furnace. During the early period of manufacture, nitrogen oxide
Nitrogen oxide
Nitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:* Nitric oxide, also known as nitrogen monoxide, , nitrogen oxide* Nitrogen dioxide , nitrogen oxide...
s were produced by the decomposition of niter at high temperature in the presence of acid, but this process was gradually supplanted by the air oxidation of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
to nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
in the presence of a catalyst. The recovery and reuse of oxides of nitrogen was an important economic consideration in the operation of a chamber process plant.
In the reaction chambers, nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
reacts with oxygen to produce nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
. Liquor from the bottom of the chambers is diluted and pumped to the top of the chamber and sprayed downwards in a fine mist. Sulfur dioxide and nitrogen dioxide are absorbed in the liquid and react to form sulfuric acid and nitric oxide. The liberated nitric oxide is sparingly soluble in water and returns to the gas in the chamber where it reacts with oxygen in the air to reform nitrogen dioxide. Some percentage of the nitrogen oxides are sequestered in the reaction liquor as nitrosylsulfuric acid
Nitrosylsulfuric acid
Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4.This salt is a source of the NO+ ion, It can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid:...
and as nitric acid, so fresh nitric oxide must be added as the process proceeds. Later versions of chamber plants included a high temperature Glover tower to recover the nitrogen oxides from the chamber liquor, while concentrating the chamber acid to as much as 78% H2SO4. Exhaust gases from the chambers are scrubbed by passing into a tower through which some of the Glover acid flows over broken tile. Nitrogen oxides are absorbed to form nitrosylsulfuric acid which is then returned to the Glover tower to reclaim the oxides of nitrogen.
Sulfuric acid produced in the reaction chambers is limited to about 35% concentration. At higher concentrations, nitrosylsulfuric acid
Nitrosylsulfuric acid
Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4.This salt is a source of the NO+ ion, It can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid:...
precipitates on the lead walls as chamber crystals
Nitrosylsulfuric acid
Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4.This salt is a source of the NO+ ion, It can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid:...
and is no longer able to catalyze
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
the oxidation reactions.
Chemistry
Sulfur dioxide is generated by burning elemental sulfurSulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
or by roasting pyritic ore
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
in a current of air:
- S8 + 8 O2 → 8 SO2
- 3 FeS2 + 8 O2 → Fe3O4 + 6 SO2
Nitrogen oxides are produced by decomposition of niter in the presence of sulfuric acid or hydrolysis of nitrosylsulfuric acid
Nitrosylsulfuric acid
Nitrosylsulfuric acid is the chemical compound with the formula NOHSO4.This salt is a source of the NO+ ion, It can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid:...
:
- 2 NaNO3 + H2SO4 → Na2SO4 + H2O + NO + NO2 + O2
- 2 NOHSO4 + H2O → 2 H2SO4 + NO + NO2
In the reaction chambers, sulfur dioxide and nitrogen dioxide dissolve in the reaction liquor. Nitrogen dioxide is hydrated to produce nitrous acid
Nitrous acid
Nitrous acid is a weak and monobasic acid known only in solution and in the form of nitrite salts.Nitrous acid is used to make diazides from amines; this occurs by nucleophilic attack of the amine onto the nitrite, reprotonation by the surrounding solvent, and double-elimination of water...
which then oxidizes the sulfur dioxide to sulfuric acid and nitric oxide. The reactions are not well characterized but it is known that nitrosylsulfuric acid is an intermediate in at least one pathway. The major overall reactions are:
- 2 NO2 + H2O → HNO2 + HNO3
- SO2 (aq) + HNO3 → NOHSO4
- NOHSO4 + HNO2 → H2SO4 + NO2 + NO
- SO2 (aq) + 2 HNO2 → H2SO4 + 2 NO
Nitric oxide escapes from the reaction liquor and is subsequently reoxidized by molecular oxygen to nitrogen dioxide. This is the overall rate determining step in the process:
- 2 NO + O2 → 2 NO2
Nitrogen oxides are absorbed and regenerated in the process, and thus serve as a catalyst
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
for the overall reaction:
- 2 SO2 + 2 H2O + O2 → 2 H2SO4