Mannheim furnace

This reaction is self-sustaining without the need for additional heating once the reactants are heated to 430—450°C 10—12% HCl is produced by this process as compared to 30—60% HCl from the Mannheim furnace process. 

This reaction takes place in a fluidized-bed reactor or a specially made furnace called a Mannheim furnace. This method was last used in the United States in the 1980s. In another process, SO2, O2, and H2O react with NaCl. 

Originally, salt and sodium bisulphate were treated in the Mannheim furnace. Sodium bisulphate was previously a residue in the manufacture of nitric acid and was used instead of sulphuric acid. Ground bisulphate was mixed with salt... 

The firm Lurgi-Chemie perfected the design of the Mannheim furnace... 

The cast iron muffle was replaced by a fireclay brick muffle. The arch was made of carborundum which conducted heat well and withstood the effect of sulphuric acid. The outer brickwork was circular in shape and not rectangular as in the Mannheim furnace. Consequently, the surface area of the muffle was smaller so that the loss of heat due to radiation was reduced to a minimum. The interchangeable blades on the four arms of the stirring device, which revolved at a velocity of 1 to 2 r. p. m., were made of carborundum which resists to wear and does not pollute the product either with iron or chromium. This is of great importance when manufacturing sulphate for glass works. 

The term salt cake generally refers to sodium sulfate, but was originally meant to be the sulfate produced in the Mannheim furnace, which yields a product containing less than percent Na2S04, compared with the much purer anhydrous Na2S04 derived from natural brines. In the latter process (shown schematically in Fig. 26.3), the natural brine, containing about 10 percent Na2S04, is saturated with... 

The Mannheim furnace process is employed to produce K2SO4 according to the following reactions ... 

See muffle furnace reverberatory furnace Mannheim furnace kiln forge cupola. 

Synthetic or manufactured sodium sulfate was originally produced in Canada in the late 1800s [41], as a by-product of the Mannheim furnace method for the production of hydrochloric acid [42]. This process consists of an acidulation step, where sodium chloride is treated with sulfuric acid at high temperatures, followed by a purification step where the crude sodium sulfate is recrystallized from water (Eqs. 6.7 and 6.8). 

The first of these reactions takes place at temperatures of about 150°C, the second reaction proceeds at about 550—660°C. Typical furnaces used to carry out the reaction include cast-iron retorts the Mannheim mechanical furnace, which consists of an enclosed stationary circular muffle having a concave bottom pan and a domed cover and the Laury furnace, which employs a horizontal two-chambered rotating cylinder for the reaction vessel. The most recent design is the Cannon fluid-bed reactor in which the sulfuric acid vapor is injected with the combustion gases into a fluidized bed of salts. The Mannaheim furnace has also been used with potassium chloride as the feed. 

FIG. 12-82 Mannheim-type mechanical hydrochloric acid furnace. 

Mannheim (1) A process for making hydrochloric acid by roasting sulfuric acid and sodium chloride together in a closed cast iron furnace equipped with a plough. The byproduct sodium sulfate, known as salt cake, may be reciystallized after neutralization and filtration, and used as a detergent ingredient. A potassium variant is used in those locations where native potassium chloride can be found. 

In the Mannheim process, NaCl and 100 percent H2S04, in amounts equivalent to complete conversion to Na2S04, are fed to a circular muffle furnace made of cast iron. The furnace is equipped with a shaft, which penetrates from below and carries four arms, each of which is fitted with two cast iron plows. The shaft rotates at 0.5 rpm, slowly plowing the heated mixture to the circumference where the burned cake discharges through a chute. The furnace charge is heated to about 840°C, just below the fusion temperature of the salt cake. HC1 is liberated, cooled, and absorbed in water to produce 32 percent HC1 for sale. The salt cake is really a byproduct of the operation. 

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