Page:Manufacture Of Soda by Hou Te-Pang.pdf/24

Rh The high price of sulfur, largely due to taxation, induced the soda manufacturers to seek a cheaper source of sulfur, and pyrites were employed, not only for its sulfur but also for the iron and copper contained in it. Here, then, a group of important products were obtained: namely, sulfuric acid, hydrochloric acid, salt cake for the glass industry, bleaching powder for the textile and paper industries, sulfur, and lastly iron and copper all clustered together around this LeBlanc soda industry.

Of great interest to students of chemical engineering was the apparatus developed in connection with the LeBlanc process. The hydrochloric acid fumes from the salt cake process discharging to the air through the chimney worked havoc on the vegetation in the vicinity. The British Government had laws known as Alkali Acts (1863, 1874), restricting the content to within 2 grains HCI per cu. ft. A coke-packed washer was invented to scrub the gas. This washer was the basis of all types of scrubbers now used in other branches of the chemical industry. In the black ash process, a revolving furnace called the "revolver" took the place of the old hand-operated furnace. This cut down the strenuous labor required of the furnace workmen and greatly increased the output. This "revolver" may be called the forerunner of the present rotary kilns employed in one style or another in so many furnacing operations. In the final drying of the monohydrate Na2CO3.H20 for soda ash, and also in the salt cake process, a mechanical furnace with a revolving bed, called McTear's furnace, was employed. For evaporating (or concentrating) the black ash liquor, and for crystallizing the monohydrate, an open Thelen pan with revolving scrapers did away with much difficulty arising from scale formation at tho bottom of the pan by the monohydrate. Without efficient stirring, a hard scale would be formed in the pan, causing the iron shell to be burned out. This Thelen pan in its closed form, which had oscillating, instead of revolving scrapers, was later introduced into the ammonia soda industry in England for calcining the bicarbonate and for recovery of the CO2 gas. Likewise, McTear's mechanical furnace was introduced for finishing soda ash or for making dense ash in the ammonia soda industry. Even up to the present time, some ammonia soda works are still using these pieces of machinery, especially in European practice. Finally, the Shank lixiviating system for black ash liquor embodied the counter-current principle that has been so widely applied in dealing with leaching and extraction processes in all modern chemical industries. All these important pieces of apparatus and some minor ones not mentioned above, our young modern chemical industries owe to the old LeBlanc eoda industry.

The LeBlanc soda industry produced a number of brilliant men whose contribution to chemical technology, either in the discovery of a chemical process or in the invention of chemical equipment, laid the foundation for many modern chemical industries. These men helped to make the LeBlanc soda industry what it was. The very difficulties these pioneers encountered and their methods of attack solved once for all, or offered solutions to, similar problems arising in other branches of chemical industry.