Carbonates lime production with

In the production of caustic soda by the action of calcium hydroxide on sodium carbonate, 1 kg/s of sodium carbonate is treated with the theoretical quantity of lime. The sodium carbonate is made up as a 20 per cent solution. The material from the extractors is fed to a countercurrent washing system where it is treated with 2 kg/s of clean water. The washing thickeners are so arranged that the ratio of the volume of liquid discharged in... 

When a kiln is used in conjunction with the Solvay process and the manufacture of soda ash, coke can be fired in the kiln along with limestone to give the larger percentages of carbon dioxide needed for efficient soda ash production. If a purer lime product is desired, the fine lime can be taken from area 4 in (Fig. 2). A less pure product is obtained from the bottom kiln section. Another kind of kiln is the rotating, nearly horizontal type. These can be as much as 12 ft in diameter and 450 ft long. Limestone enters one end. It is heated, rotated, and slowly moves at a slight decline to the other end of the kiln, where lime is obtained. 

Preliming. A small amount of lime (0.12-0.3% CaO is added to the juice, increasing the juice pH from about 6.2 to 10.8-11.4. The lime reacts with nonsugar impurities in the juice to make insoluble precipitates and soluble products. Calcium carbonate in the form of recycled first carbonation sludge is added to provide colloid adsorption and stabilization. Temperature may be cool (50°C) or hot (80°C) depending on the factory design. Insoluble precipitates are formed quickly. Retention time is 15-30 minutes. 

It should be noted that lime reacts with clay particles. This leads to strength increase by pozzolanic and carbonation cementation processes. Cation exchange and pozzolanic reactions result in strength increase. The level of reactivity and hence strength gained in soil-lime mixtures depends on the level of pozzolanic product created. The chemical reaction between soil and lime can be presented as below ... 

In the Kraft recovery process the green liquor, which is an aqueous solution of sodium carbonate, is heated with lime to produce white liquor or caustic soda, which is then returned to the pulp digestion operations. In the production of alumina, lime and soda are fed to bauxite digesters. The CaCO 3 produced during the course of the reaction is rebumed to lime and is recycled. The main difficulties associated with these processes include the extensive mechanical handling through the use of causticizers, settlers, and repulpers in order to produce caustic that is low in carbonate and the high fuel consumption needed to reconvert CaCO to lime. 

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