The Lead Chamber Process

At first it was not known that niter, which was an essential part of the lead chamber process, acted as a catalyst. When Lavoisier showed that sulfuric acid contained only sulfur, oxygen, and hydrogen (1772-1777) it was realized that niter was not a component of chamber acid. Operators then assumed that it either made the sulfur flame hotter or supplied oxygen to the sulfurous acid. 

At that time, acid was still being made in batches and no air was added to the lead house during reaction. By 1793 Clement and Desormes had suggested that the continuous addition of air would improve reaction, and in 1806 they defined the action of niter, which was clearly essential to the process  

Clement and Desormes were also the first to observe the formation of chamber crystals that evolved nitric oxide and formed sulfuric acid when added to water. The nitric oxide was then available for recycling. 

1666 Fevre and Lemery Sulfur burned with saltpeter (KNOj)  

1749 Roebuck and Garbutt, Prestonpans, Scotland. Used lead chambers. 1-lb KNO3 with 7-lb sulfur every 4 hours on iron trays. Air replenished between batches of sulfur. Acid gravity usually 1.250 (33%) after six weeks Concentrated to almost 50%. Yield about 110% based on sulfur. Several hundred chambers used at each site 70,000 ft (200 m ) at Prestonpans. 

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Figure 10.5. The Lead Chamber process for the manufacture of sulphuric acid...

Sulfonic acids containing nitrogen have long been implicated as essential intermediates in the synthesis of H2SO4 by the lead-chamber process (p. 708) and, as shown by F. Seel and his group, the crucial stage is the oxidation of sulfite ions by the nitrosyl ion NO+ ... 

Nitrose, /. (Sulfuric Acid) a solution of nitro-sylsulfuric acid in sulfuric acid, formed in the lead-chamber process. 

The older process is called the lead chamber process. It uses a mixture of gaseous oxides of nitrogen—nitric oxide, NO, and nitrogen dioxide, N02—as the catalyst. This process has been in use and under development for over 200 years. It is named after the large room-like chambers lined with lead in which the gaseous reactions are carried out. The lead walls react with the acid and become coated with an inert protective coating of lead sulfate. 

It is believed that H2S04 was discovered in about the 10th century. In the 1800s most of the H2S04 was produced by the lead chamber process, although it was also produced by pyrolysis of FeS04-xH20. 

To date, the single most important commercial use of lead is in the manufacture of lead-acid storage batteries. However, for most of the twentieth century, the most important environmental source of Pb was gasoline combnstion. It is also used in alloys, such as fusible metals, antifriction metals, and solder. Lead foil is made with lead alloys. Lead is used for covering cables and as a lining for laboratory sinks, tanks, and the chambers in the lead-chamber process for the manufacture of sulfuric acid. It is used extensively in plumbing. Because it has excellent vibration-dampening characteristics, lead is often used to support heavy machinery. 

Late 1800s The lead chamber process for manufacturing sulfuric acid was prevalent in this period. Arsenic was a common contaminant in the pyrites used as a source of sulfur for this process. Now the cleaner contact process is used and most of the raw material is elemental sulfur. 

Nitrosylsulfuric acid is produced as an intermediate in the manufacture of sulfuric acid using the lead chamber process by the reaction of sulfur dioxide, nitrogen dioxide, oxygen, and water. 

While the lead-chamber process increased the amount of sulfuric acid that could be produced, it relied on a source of nitrate that usually had to be imported. The process also produced nitric oxide gas, NO, which oxidized to brown nitrogen dioxide in the atmosphere. To reduce the supply of nitrate required and the amount of nitric oxide produced, Gay-Lussac proposed that the nitric oxide be captured in a tower and recycled into the lead chamber. Although Gay-Lussac first proposed this modification to the lead-chamber method around 1830, it was not until the 1860s that John Glover (1801-1872) actually implemented Gay-Lussac s idea with the Glover tower. 

The lead-chamber process supplied the world s need for sulfuric acid for a century and a half. In the late nineteenth century, the contact process replaced the lead-chamber process. The contact process utilized sulfur dioxide, SOj, which was produced as a byproduct when sulfur-bearing ores were smelted. The contact process was named because the conversion of sulfur dioxide to sulfur trioxide, SO3, takes place on contact with a vanadium or platinum catalyst during the series of reactions ... 

As noted in Section 8.5, there are two important complications in the conversion of S02 to liquid H2S04 the oxidation of S02 is generally slow and must be catalyzed, and the direct reaction of SO3 with water tends to produce intractable aerosols (mists) of H2S04. The lead chamber process, which dates back to 1746, employs nitrogen oxides as the catalyst the intermediate HO—S02—O—NO, or nitrosylsulfuric acid, is easily... 

The reaction is exothermic (see Exercise 12.1), but, since it is very slow, a catalyst is necessary. Nitric oxide, once again, can serve as an oxygen carrier, as in the lead chamber process (Section 10.2) and in reaction 10.8, where (CH3)2S generated in the kraft process is converted to DMSO. Even so, at the elevated temperatures required, reaction 12.1 needs to be forced to completion by absorption of the steam in concentrated sulfuric acid or some other desiccant. In variants of the Deacon process, copper chloride acts as the catalyst or as an intermediate for chlorine regeneration. 

This commonest derivative of sulphur trioxide and the most important of all acids from a technical and commercial aspect, has been known from early times, although its production on a large scale and at a low price dates from the success of the lead chamber process of manufacture, which revolutionised chemical industry in the early part of the nineteenth century. 

The Pyrites Burners.—In the lead chamber process the first chemical action is the oxidation of sulphur to sulphur dioxide by atmospheric oxygen. The iron pyrites (or free sulphur, spent oxide from the gas works, or other sulphides such as zinc blende, as the case may be) is placed on shelves or bars in a series of ovens of suitable type. When iron pyrites or sulphur is used, the combustion when once started proceeds to completion without further assistance by external heat ... 

Nitrosulphonic Acid, Nitrosylsulphuric Acid or Nitroso-sulphuric Acid, NQ2.S02.0H.—In 1806, Clement and Desormcs, during the manufacture of sulphuric acid by the lead chamber process, observed the formation of a crystalline solid, to which the names nitrosulphonic acid and nitrosylsulphuric acid were later given the term chamber crystals, however, is still commonly applied to this acid.6 The composition and nature of the acid were first investigated by Weber,7 and by Michaelis and Schumann.8... 

It is fairly generally believed that nitrosulphonic acid plays an important part in the lead chamber process for the manufacture of sulphuric acid (see p. 153). The vapour pressures of mixtures of sulphuric acid with nitrous or nitric acid or with both these acids, within the range occurring in the chambers, increase with the nitrogen acid content and with rise in temperature, and the total pressure is always higher than the sum of the individual pressures, especially when the sulphuric acid is concentrated, for nitric acid - sulphuric acid mixtures this may be explained 1 by the occurrence of the following... 

Lead-chamber process. The essential features of the lead-chamber process are the use of nitric acid to oxidize S02 to S03 and the absorption of S03 by water in large absorber towers. This process has been used for well over 100 years, and the details of equipment and operation are essentially the same today as when the process was first designed. 

The lead-chamber process is more economical than the contact process, but it produces a more dilute and less pure product. Thus, the chamber process can compete only in the market that can use a relatively impure and dilute acid. Although chamber-acid plants now in use will undoubtedly be operated for many years to come, it seems probable that all sulfuric acid plants constructed in the future will employ the contact process or some still more efficient process. 

The manufacture of sulfuric acid by the lead chamber process involves oxidation of sulfur to sulfur dioxide by oxygen, further oxidation of sulfur dioxide to sulfur trioxide with nitrogen dioxide, and, finally, hydrolysis of sulfur trioxide. 

In the 1800s, the most important method for producing H2S04 was by the lead chamber process. Today, sulfuric acid is produced by a method known as the contact process. In the contact process, sulfur is burned to give S02 or the required S02 is recovered from coal burning or ore roasting processes. The S02 is then oxidized in the presence of a catalyst to produce SO3 (see Section 15.7.2). Typical catalysts are spongy platinum or sodium vanadate. Next, the SO3 is dissolved in 98% sulfuric acid ... 

Roebuck introduces the lead chamber process for H2SO4... 

SO2 is oxidized by nitric oxides, as exemplified in the Lead Chamber Process (equation 15). This process is only operated in special cases nowadays, because of the low final acid concentration that is achievable (no more than 78%), although it only requires modest temperatures and so may be utilized again in the future. 

The Manufacture of Sulfuric Acid. Sulfuric acid is made by two processes, the contact process and the lead-chamber process, which are now about equally important. 

The principle of the lead-chamber process is shotvn by the following experiment (Fig. 17-5). A large flask is fitted with four inlet tubes... 

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