Continuous process for the manufacture of calcium magnesium acetate deicer

Abstract

Finely divided lime, at any degree of slaking, is introduced in a steady stream into an agitated reactor designed to produce pellets or aggregates. Concentrated acetic acid is simultaneously introduced in a steady stream at a rate equal to the chemical combining rate required to produce calcium magesium acetate. Water content of the reaction stream is critical; the mol ratio of water, including water of neutralization, to the calcium magnesium acetate product must fall in the range 3.3-7.0 in order to form the desired pellets and to avoid sticking, caking, and dust emanation from the reactor. Product pellets are drawn off in a stream from the reactor and dried for use as a non-polluting roadway and walkway deicer. Traction agent is optionally incorporated into the deicer pellets by introducing a steady stream of traction agent to the reactor simultaneous with raw materials introduction. Magnesium-to-calcium ratios greater than one are achieved by blending dolime with magnesium-rich ore.

I claim: 
     
       1. A process for the manufacture of coarse-particle calcium magnesium acetate characterised in that aqueous acetic acid is combined with the stoichiometric requirement of lime in a suitable agitated reaction vessel, wherein the water content of the reaction mass is critically controlled .[.such that the mol ratio of water to calcium acetate in said reaction mass does not exceed about 3.3,.]. and the resulting damp product of reaction is dried to produce the final product, the improvement comprising: (a) introducing finely divided lime at a constant rate to said agitated reaction vessel:   (b) simultaneously introducing concentrated aqueous acetic acid solution at a constant rate to said reaction vessel wherein the ratio of acid rate, anhydrous acid basis, to the lime rate, active lime basis, is equal to the stoichiometric chemical combining ratio;   (c) maintaining the mol ratio of water input regardless of source, to the acetic acid input, anhydrous acid basis, within the range 0.75-1.15;   (d) withdrawing the damp, coarse-particle product formed in said vessel at steady-state; and   (e) drying the product of Step d.   
     
     
       2. The process of claim 1 wherein said lime is unslaked. 
     
     
       3. The process of claim 1 wherein said lime is partially slaked. 
     
     
       4. The process of claim 1 wherein said lime is completely slaked. 
     
     
       5. The process of claim 1 wherein the mol ratio of magnesium to calcium in said lime is controlled within the range 0-0.1. 
     
     
       6. The process of claim 1 wherein the mol ratio of magnesium to calcium in said lime is controlled within the limits 0.1-1.0. 
     
     
       7. The process of claim 1 wherein the mol ratio of magnesium to calcium in said lime is 1.0. 
     
     
       8. The process of claim 1 wherein essentially all hydrate water is driven off in step e. 
     
     
       9. The process of claim 7 wherein drying is incomplete, to the degree that 0-3.5 mols of water per mol of calcium magnesium acetate are allowed to remain with the product. 
     
     
       10. The process of claim 1 wherein the ratio of acid to lime inputs is 100-1.05 times the stoichiometric chemical combining ratio. 
     
     
       11. A process for the manufacture of coarse-particle calcium magnesium acetate characterised in that aqueous acetic acid is combined with the stoichiometric requirement of lime in a suitable agitated reaction vessel, wherein the water content of the reaction mass is critically controlled .[.such that the mol ratio of water to calcium acetate in said reaction mass does not exceed about 3.3,.]. and the resulting damp product of reaction is dried to produce the final product, the improvement comprising: (a) blending finely divided dolomite lime with a finely divided magnesium-rich ore such that the Mg/Ca mol ratio in the resulting blend falls in the range of 1-2;   (b) introducing said blend at a constant rate to a suitable agitated reaction vessel;   (c) simultaneously introducing concentrated aqueous acetic acid at a constant rate of said vessel, wherein the ratio of acid rate to ore-blend rate is equal to the chemical combining ratio;   (d) maintaining the mol ratio of total water input to acid input within the range of 0.75-1.17;   (e) withdrawing the damp-coarse-particle product formed in said reaction vessel, at steady-state; and   (f) drying the product of Step e.   
     
     
       12. The process of claim 1 wherein traction agent is simultaneously introduced into the reaction vessel at a constant rate such that the weight ratio of said traction agent to final dried product falls in the range 10-90%. 
     
     
       13. The process of claim 11 wherein traction agent is simultaneously introduced into the reaction vessel at a constant rate such that the weight ratio of said traction agent to final dried product falls in the range of 10-90%. .Iadd.14. The process of claim 11 wherein drying is incomplete, to the degree that 0-3.5 mols of water per mol of magnesium acetate are allowed to remain with the product. .Iaddend.