Coal-water fuel slurries and process for making

Claim 2

A coal-water fuel slurry which comprises: a, finely-divided coal having a particle size distribution which is 100% -50 mesh (-297µ) and at least 50% -200 mesh(-74µ) said coal being in amount sufficient to provide a desired coal concentration in the slurry; b. a minor amount of anionic monovalent cation salt organic dispersant sufficient to reduce substantially the viscosity of the slurry; c. a minor amount of anionic alkaline earth metal salt organic dispersant sufficient to produce a slurry yield point larger than that obtained with said monovalent cation salt alone and to maintain the slurry in substantially stable static dispersion; and d. water.

Claim 3

A slurry according to claim 1 in which the monovalent cation is an alkali metal.

Claim 4

A slurry according to claim 1 or 2 in which the finely- divided coal has a particle size distribution of which at least 65% is -200 mesh (-74µ).

Claim 5

A slurry according to any one of claims 1 to 3 in which the alkaline earth metal salt dispersant is an organosulfonate.

Claim 6

A slurry according to claim 4 in which the alkaline earth metal dispersant is a Ca lignosulfonate..

Claim 7

A slurry according to any one of claims 1 to 5 in which the monovalent cation salt dispersant is an organosulfonate.

Claim 8

A slurry according to claim 6 in which the monovalent cation salt dispersant is a Na or K lignosulfonate.

Claim 9

A slurry according to any one of claims 1 to 7 in which the coal particle sizes comprise:

Claim 10

a. fine particles having a maximum size of 30µ MMD (Mass Median Diameter) in an amount comprising from 10 to 50% by weight of the slurry, and b. larger coal particles within the size range of from 20 to 200µ MMD, in which sub-sieve particle sizes are defined in terms of those obtainable by forward scattering optical counter.

Claim 11

a. fine particles having a maximum size of 30µ MMD (Mass Median Diameter) in an amount comprising from 10 to 50% by weight of the slurry, and b. larger coal particles within the size range of from 20 to 200µ MMD, in which sub-sieve particle sizes are defined in terms of those obtainable by forward scattering optical counter.

Claim 12

A slurry according to claim 8 in which the fine particles comprise from 10 to 30% by weight thereof.

Claim 13

A slurry according to claim 8 or 9 in which the size range of the fine coal particles is from 1 to 15µ MMD and the size range of the larger coal particles is from 20 to 150µ MMD.

Claim 14

A process for making a substantially stable coal-water fuel slurry, which comprises: a, admixing: (i) finely-divided coal having a particle size distribution which is 100% -50 mesh (-297µ) and at leasr 50% -200 mesh (-74µ) said coal being in amount sufficient to provide a desired coal concentration in the slurry; (ii) a minor amount of anionic monovalent cation salt organic dispersant sufficient to reduce substantially the viscosity of the slurry; (iii) a minor amount of anionic alkaline earth metal salt organic dispersant sufficient to produce a slurry yield point larger than that obtained with said monovalent cation salt dispersant alone and to maintain the slurry in substantially stable static dispersion; and (iv) water, and b. subjecting the mixture to high shear mixing at a shear rate of at least 100 sec -1 .

Claim 15

A process for making a substantially stable coal-water fuel slurry, which comprises: a, admixing: (i) finely-divided coal having a particle size distribution which is 100% -50 mesh (-297µ) and at leasr 50% -200 mesh (-74µ) said coal being in amount sufficient to provide a desired coal concentration in the slurry; (ii) a minor amount of anionic monovalent cation salt organic dispersant sufficient to reduce substantially the viscosity of the slurry; (iii) a minor amount of anionic alkaline earth metal salt organic dispersant sufficient to produce a slurry yield point larger than that obtained with said monovalent cation salt dispersant alone and to maintain the slurry in substantially stable static dispersion; and (iv) water, and b. subjecting the mixture to high shear mixing at a shear rate of at least 100 sec -1 .

Claim 16

A process according to claim 11 in which the coal particle sizes comprise: a. fine particles having a maximum size of 30µ MMD in an amount comprising from 10 to 50% by weight of the slurry; and b. larger coal particles within the size range of from 20 to 200µ MMD; in which sub- sieve particle sizes are defined in terms of those obtainable by forward scattering optical counter.

Claim 17

A process according to claim 11 or 12 in which the fine particles comprise from 10 to 30% by weight of the slurry.

Claim 18

A process according to any one of claims 11 to 13 in which the size range of the fine particles is from 1 to 15µ MMD and the size range of the larger particles is from 20 to - 150µ MMD.

Claim 19

A process for converting a coal-water pipeline slurry into a substantially stable fuel slurry, wherein the pipeline slurry contains particles of excessive size for efficient combustion, which comprises: a. partially dewatering or addingfinely-divided coal in an amount sufficient to increase the coal content in the pipeline slurry to a concentration desired in the fuel slurry, if the coal concentration in the aqueous pipeline slurry is less than that desired in the fuel slurry; b. passing said slurry through a comminuting means to reduce excessively sized coal particles to sizes sufficiently small for combustion in a combustion chamber and to produce a particle size distribution of 100% -50 mesh (-297µ) and at least 50% -200 mesh (-74µ). c. adding to the slurry a minor amount of: (i) an anionic monovalent cation salt organic dispersant sufficient to reduce substantially the viscosity of the slurry, and (ii) an alkaline earth metal salt organic dispersant sufficient to produce a slurry yield point larger than that produced with said monovalent cation dispersant alone and to maintain the slurry in a substantially stable static dispersion; and d. subjecting the mixture comprising said coal, said monovalent cation and alkaline earth metal dispersants and water to high shear mixing at a shear rate of at least about 100 sec -1 .

Claim 20

A process for converting a coal-water pipeline slurry into a substantially stable fuel slurry, wherein the pipeline slurry contains particles of excessive size for efficient combustion, which comprises: a. partially dewatering or addingfinely-divided coal in an amount sufficient to increase the coal content in the pipeline slurry to a concentration desired in the fuel slurry, if the coal concentration in the aqueous pipeline slurry is less than that desired in the fuel slurry; b. passing said slurry through a comminuting means to reduce excessively sized coal particles to sizes sufficiently small for combustion in a combustion chamber and to produce a particle size distribution of 100% -50 mesh (-297µ) and at least 50% -200 mesh (-74µ). c. adding to the slurry a minor amount of: (i) an anionic monovalent cation salt organic dispersant sufficient to reduce substantially the viscosity of the slurry, and (ii) an alkaline earth metal salt organic dispersant sufficient to produce a slurry yield point larger than that produced with said monovalent cation dispersant alone and to maintain the slurry in a substantially stable static dispersion; and d. subjecting the mixture comprising said coal, said monovalent cation and alkaline earth metal dispersants and water to high shear mixing at a shear rate of at least about 100 sec -1 .

Claim 21

A process according to claim 15 in which at least some of the monovalent cation dispersant is a component of the pipeline slurry.

Claim 22

A process according to any one of claims 11-16 in which the monovalent cation is an alkali metal.

Claim 23

A process according to any one of claims 11-17 in which the finely-divided coal has a particle size distribution of which at least 65% is -200 mesh (-74µ).

Claim 24

A process according to any one of claims 11-18 in which the alkaline earth metal salt is an organosulfonate.

Claim 25

A process according to claim 19 in which the alkaline earth metal salt is a Ca lignosulfonate.

Claim 26

A process according to any one of claims 11-20 in which the monovalent cation dispersant is an organosulfonate.

Claim 27

A process according to claim 21 in which the monovalent cation dispersant is a Na or K lignosulfonate.