Carbon Dioxide → Calcium Carbonate

HRID 343267Notes

Reaction equation

HRID 343267 reaction equation
[O-2:1].[Ca+2:2].C(=O)=[O:4].[C:6]([O-:9])([O-:8])=[O:7].[Ca+2]>O>[OH-:4].[Ca+2:2].[OH-:7].[OH2:1].[C:6]([O-:9])([O-:8])=[O:7].[Ca+2:2]

Participants

6

Reactant 3

HCID 280Carbon DioxideHCID 10112Calcium CarbonateHCID 6850728Calciumoxide2×

Product 2

HCID 10112Calcium CarbonateHCID 5289063Calcium hydroxide​, monohydrate

Reagents, catalysts & solvents 1

HCID 962WaterSolvent2×

Procedure

To prepare the aragonitic precipitated calcium carbonate of the invention, a milk of lime (Ca(OH)2) slurry or slake is prepared by adding water to calcium oxide (CaO) with agitation. Preferably, about ten parts water having a temperature of at least about 40° C. (Centigrade) is added to one part CaO to produce a slake having a solids content of about 11 percent, based on the weight of Ca(OH)2 in the solution. The slake is screened to remove grit, typically with a screen that will remove grit of about +60 mesh, and the slake temperature is adjusted to about 50° C. Dry aragonite, such as M60 Aragonite from the Mississippi Lime Company, located in St. Genevieve, Mo., is added, and the slake is agitated for about 15 minutes. Preferably, the amount of aragonite added is equivalent to about five percent of the total amount of precipitated calcium carbonate that will be produced from the slake. Carbon dioxide gas is then added with vigorous agitation. The gas stream rate should be sufficient to convert substantially all of the Ca(OH)2 to CaCO3 in about three hours, forming a precipitated calcium carbonate slurry of about 14 percent solids. Carbonation is complete when the pH falls to 7, at which time the carbon dioxide (CO2) stream is terminated. Typically, between about 9 ft3 and 10 ft3 of CO2 are required for each kilogram of precipitated calcium carbonate produced. The product can then be dewatered to a concentration of about 70 percent solids to produce a cake that can be treated with a typical dispersant, e.g., sodium polyacrylate, and dispersed on a flat-blade or similar dispersion unit.

Workup

  1. customTo prepare the aragonitic
  2. customprecipitated calcium carbonate of the invention
  3. customto produce a slake
  4. customto remove grit
  5. customtypically with a screen that will remove grit of about +60 mesh
  6. customis adjusted to about 50° C
  7. addition, is added
  8. additionPreferably, the amount of aragonite added
  9. customwill be produced from the slake
  10. customin about three hours

Sources & evidence

ORD record
ord-8f898d0456e64d5fabf580e76aa9f08b
Source dataset
uspto-grants-1999_01
Patent number
US05861209

Reaction notes

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