Highly porous powdered slaked lime composition

Abstract

The present invention concerns a powdery slaked lime composition having an Alpine fluidity greater than 50% and including a first fraction of particles having a size less than 32 μm and a second fraction of particles with the size greater than 32 μm, the second fraction being less than 10% by weight, compared to the total weight of the composition. The invention also relates to a method for producing same.

Claims

1. Powdery slaked lime composition having a BET specific surface, obtained by nitrogen adsorption, greater than or equal to 25 m.sup.2/g and a total BJH pore volume, constituted of pores the diameters of which are less than 1000 Å, obtained by nitrogen desorption, greater than or equal to 0.15 cm.sup.3/g, characterised in that this composition possesses in addition an Alpine fluidity greater than 50%, the Alpine fluidity AF being defined by the equation: $\mathrm{AF}=\frac{m_i-m_{R90\left(T15;P100\right)}}{m_i-m_{R90\left(T120;P150\right)}}.Math.100\%$ where: m.sub.i is an initial mass of 50 g of powder spread over a 90 μm sieve; m.sub.R90(T15;P100) is a mass of residues of material left on the sieve after 15 seconds with a depression of 100 mm of manometric liquid, the density of which is 0.88; m.sub.R90(T120;P150) is a mass of residues of material left on the sieve after 15 seconds with a depression of 100 mm of manometric liquid, the density of which is 0.88, and after 120 seconds with the depression at 150 mm of manometric liquid with a density of 0.88; and the aforementioned composition includes a first fraction of particles having a size less than 32 μm and a second fraction of particles with the size greater than 32 μm, the second fraction of particles being less than 10% by weight, compared to the total weight of the composition, said powdery slaked lime composition further comprises residual organic solid additives coming from organic additives selected from the group consisting of mono- or poly-ethylene glycol and their mixtures.

2. The powdery slaked lime composition according to claim 1, presenting in addition a non-solid residual phase content, measured by a loss of ignition test at 180° C., greater than or equal to 0.3% compared to the total weight of powdery slaked lime composition.

3. Powdery slaked lime composition according to claim 2, in which the said non-solid residual phase includes water and/or residual additives, such residual additives being inorganic and/or organic additives, free or linked to the lime compound.

4. The powdery slaked lime composition according to claim 1, presenting in addition a non-solid content in residual phase, measured by a loss of ignition test at 110° C., less than or equal to 3.5% by weight and greater than 0% by weight compared to the total weight of the powdery slaked lime composition.

5. The powdery slaked lime composition according to claim 1, presenting in addition a particle size d.sub.50 less than or equal to 8 μm.

6. The powdery slaked lime composition according to claim 1, characterised in that the said composition has a BET specific surface obtained by the adsorption of nitrogen greater than or equal to 30 m.sup.2/g.

7. The powdery slaked lime composition according to claim 1, characterised in that the said composition has a BET specific surface obtained by the adsorption of nitrogen less than or equal to 55 m.sup.2/g.

8. The powdery slaked lime composition according to claim 1, characterised in that the said composition has a total BJH pore volume made up of pores having a diameter less than 1000 Å, obtained by nitrogen desorption, greater than or equal to 0.17 cm.sup.3/g.

9. The powdery slaked lime composition according to claim 1, characterised in that the said composition has a total BJH pore volume made up of pores having a diameter less than 1000 Å, obtained by nitrogen desorption, less than or equal to 0.30 cm.sup.3/g.

10. The powdery slaked lime composition according to claim 1, characterised in that the said compound has a BJH pore volume made up of pores having a diameter between 100 and 300 Å, obtained by nitrogen desorption, greater than or equal to 0.07 cm.sup.3/g and less than 0.15 cm.sup.3/g.

11. Composition of industrial sorbent including at least the said powdery slaked lime composition according to claim 1.

Description

EXAMPLE 1

(1) A highly porous and fine powdery slaked lime composition according to the present invention is produced industrially by mixing water and quicklime (2.7 t/h of quicklime) in a hydrator, in quantities such that the product leaves the hydrator with a non-solid residual phase, measured by a loss of ignition (LOI) test at 180° C., comprised between 22 and 24% by weight. 0.2% of diethylene glycol (expressed as % by weight of quicklime) is added to the slaking water before hydration. The wet slaked lime which leaves the hydrator in then transported towards a pin mill into which hot air is injected in order to instantly dry the wet slaked lime and to produce the highly porous powdery slaked lime before storage.

(2) The resulting powdery slaked lime composition has an Alpine fluidity of 51%, a d.sub.50 of 4.2 μm and a particle fraction the size of which is greater than 32 μm (R.sub.32) and is 6.2% by weight. Its specific surface and total pore volume are respectively 41.1 m.sup.2/g and 0.214 cm.sup.3/g.

(3) Even though the preferred production modes of the invention have been described as an illustration, the knowledgeable tradesman knows that various modifications, additions or substitutions are possible, without moving away from the spirit of the invention such as described in the claims appendices.