Process for the liquefaction of coal

Claim 2

In a coal liquefaction process wherein a liquefaction solvent that is at least partially distillable is used in a liquefaction zone to yield a product from which a slurry is recovered that comprises distillable and substantially nondistillable coal liquefaction products and an insoluble residue, the improvement which comprises: contacting said slurry with a first extraction solvent comprising a polycyclic aromatic hydrocarbon containing at least one less substituted or unsubstituted carbon atom than said liquefaction solvent at a first elevated temperature level and pressure level such that the reduced temperature of said first extraction solvent is greater than about 0.7 and the reduced pressure of said first extraction solvent is greater than about 0.4 to effect a separation of said slurry into a substantially solids-free fraction comprising coal liquefaction products and first extraction solvent and a solids-containing fraction; separating at least a portion of said first extraction solvent from said substantially solids-free fraction to provide a first extraction solvent-lean coal liquefaction product fraction; contacting said first extraction solvent-lean coal liquefaction product fraction with a second extraction solvent having at least one less substituted or unsubstituted carbon atom than said first extraction solvent at a second elevated temperature level and pressure level such that the reduced temperature of said second extraction solvent is greater than about 0.7 and the reduced pressure of said second extraction solvent is greater than about 0.4 to effect a separation of said coal liquefaction products into a second light phase and a second heavy phase comprising substantially nondistillable coal-derived compounds at least a portion of which are capable of functioning as a coal solvent and some second extraction solvent; recovering said substantially nondistillable coal-derived compounds; and introducing at least a portion of said substantially nondistillable coal-derived compounds into said liquefaction zone to supplant a portion of said liquefaction solvent in said liquefaction process.

Claim 3

The process of claim 1 wherein said first extraction solvent comprises a polycyclic aromatic hydrocarbon containing at least two fused benzene rings.

Claim 4

The process of claim 1 wherein the conditions of temperature and pressure at which the first extraction solvent contacts the slurry are such that the reduced temperature of said first extraction solvent is in the range of from about 0.7 to about 1.5 and the reduced pressure is in the range of from about 0.4 to about 10.

Claim 5

The process of claim 1 wherein the conditions of temperature and pressure at which the first extraction solvent contacts the slurry are such that the reduced temperature of said first extraction solvent is in the range of from about 0.8 to about 1.25 and the reduced pressure is in the range of from about 0.4 to about 5.0.

Claim 6

The process of claim 1 wherein the second extraction solvent contains at least one less benzene ring than the first solvent.

Claim 7

The process of claim 1 wherein separating said first extraction solvent from said substantially solids-free fraction is defined further as effected by flashing.

Claim 8

The process of claim 1 wherein the second elevated temperature level is a temperature greater than the first elevated temperature level.

Claim 9

The process of claim 1 wherein the conditions of temperature and pressure at which the second extraction solvent contacts said first extraction solvent-lean coal liquefaction product fraction are such that the reduced temperature of said second extraction solvent is in the range of from about 0.7 to about 1.5 and the reduced pressure is in the range of from about 0.4 to about 10.

Claim 10

The process of claim 1 wherein the conditions of temperature and pressure at which the second extraction solvent contacts said first extraction solvent-lean coal liquefaction product fraction are such that the reduced temperature of said second extraction solvent is in the range of from about 0.8 to about 1.25 and the reduced pressure is in the range of from about 0.4 to about 5.0.

Claim 11

The process of claim 1 defined further to include the steps of: separating at least a portion of said second extraction solvent from said second light phase to provide a second extraction solvent-lean coal liquefaction product fraction; contacting said second extraction solvent-lean coal liquefaction product fraction with a third extraction solvent having at least one less substituted or unsubstituted carbon atom than said second extraction solvent at a third elevated temperature level and pressure level such that the reduced temperature of said third extraction solvent is greater than about 0.7 and the reduced pressure of said third extraction solvent is greater than about 0.4 to effect a separation of said second solvent-lean coal liquefaction product fraction into a third light phase and a third heavy phase; recovering said third heavy phase; increasing the temperature level of said third light phase to a fourth temperature level above said third temperature level at which said third light phase is formed to effect a separation of said third light phase into a fourth light phase comprising said third extraction solvent and a fourth heavy phase; recovering said fourth heavy phase; and recycling said fourth light phase to provide at least a portion of said third extraction solvent for contacting the second solvent-lean coal liquefaction product fraction.

Claim 12

The process of claim 10 wherein the third elevated temperature level and pressure level is above the critical temperature and pressure of the third extraction solvent.

Claim 13

The process of claim 1 wherein the second elevated temperature level and pressure level is above the critical temperature and pressure of the second extraction solvent.

Claim 14

The process of claim 1 defined further to include the step of: hydrotreating at least a portion of said substantially nondistillable coal-derived compounds prior to introduction into said liquefaction zone.

Claim 15

In a coal liquefaction process wherein a liquefaction solvent that is at least partially distillable is used in a liquefaction zone to yield a product from which a slurry is recovered that comprises distillable and substantially non-distillable coal liquefaction products and an insoluble residue, the improvement which comprises: contacting said slurry with a first extraction solvent comprising a fluid containing at least one less substituted or unsubstituted carbon atom than said liquefaction solvent at a first elevated temperature level and pressure level such that the reduced temperature of said first extraction solvent is greater than about 0.7 and the reduced pressure of said first extraction solvent is greater than about 0.4 to effect a separation of said slurry into a first light phase comprising at least a portion of said distillable and substantially nondistillable coal liquefaction products and first extraction solvent and a first heavy phase comprising insoluble residue, any remaining substantially nondistillable coal liquefaction products and some first extraction solvent; contacting said first heavy phase with a second extraction solvent comprising a fluid having at least one more substituted or unsubstituted carbon atom than said first extraction solvent and at least one less substituted or unsubstituted carbon atom than said liquefaction solvent at a second elevated temperature level and elevated pressure level such that the reduced temperature level of said second extraction solvent is greater than about 0.7 and the reduced pressure of said second extraction solvent is greater than about 0.4 to effect a separation of at least a portion of any remaining substantially nondistillable coal liquefaction products in said first heavy phase into a second light phase comprising substantially nondistillable coal liquefaction products including substantially nondistillable coal-derived compounds at least a portion of which are capable of functioning as a coal solvent and second extraction solvent and a second heavy phase comprising insoluble residue, any remaining coal liquefaction products and some second extraction solvent; and introducing at least a portion of said substantially nondistillable coal-derived compounds into said liquefaction zone to supplant a portion of said liquefaction solvent in said liquefaction process.

Claim 16

In a coal liquefaction process wherein a liquefaction solvent that is at least partially distillable is used in a liquefaction zone to yield a product from which a slurry is recovered that comprises distillable and substantially non-distillable coal liquefaction products and an insoluble residue, the improvement which comprises: contacting said slurry with a first extraction solvent comprising a fluid containing at least one less substituted or unsubstituted carbon atom than said liquefaction solvent at a first elevated temperature level and pressure level such that the reduced temperature of said first extraction solvent is greater than about 0.7 and the reduced pressure of said first extraction solvent is greater than about 0.4 to effect a separation of said slurry into a first light phase comprising at least a portion of said distillable and substantially nondistillable coal liquefaction products and first extraction solvent and a first heavy phase comprising insoluble residue, any remaining substantially nondistillable coal liquefaction products and some first extraction solvent; contacting said first heavy phase with a second extraction solvent comprising a fluid having at least one more substituted or unsubstituted carbon atom than said first extraction solvent and at least one less substituted or unsubstituted carbon atom than said liquefaction solvent at a second elevated temperature level and elevated pressure level such that the reduced temperature level of said second extraction solvent is greater than about 0.7 and the reduced pressure of said second extraction solvent is greater than about 0.4 to effect a separation of at least a portion of any remaining substantially nondistillable coal liquefaction products in said first heavy phase into a second light phase comprising substantially nondistillable coal liquefaction products including substantially nondistillable coal-derived compounds at least a portion of which are capable of functioning as a coal solvent and second extraction solvent and a second heavy phase comprising insoluble residue, any remaining coal liquefaction products and some second extraction solvent; and introducing at least a portion of said substantially nondistillable coal-derived compounds into said liquefaction zone to supplant a portion of said liquefaction solvent in said liquefaction process.

Claim 17

The process of claim 14 defined further to include the step of: hydrotreating at least a portion of said substantially nondistillable coal-derived compounds prior to introduction into said liquefaction zone.

Claim 18

The process of claim 14 wherein the second elevated temperature level and pressure level are above the critical temperature and pressure of the second extraction solvent.

Claim 19

The process of claim 14 defined further to include the steps of: heating said second light phase to a temperature level above the second temperature level while maintaining said second light phase at an elevated pressure level to effect a separation of said second light phase into a third light phase comprising second extraction solvent and a third heavy phase comprising substantially nondistillable coal liquefaction products including said substantially nondistillable coal-derived compounds; and introducing at least a portion of said substantially nondistillable coal-derived compounds of said coal liquefaction products into said liquefaction zone to supplant a portion of said liquefaction solvent.

Claim 20

The process of claim 14 wherein the conditions of temperature and pressure at which the first extraction solvent contacts the slurry are such that the reduced temperature of said first extraction solvent is in the range of from about 0.9 to about 1.5 and the reduced pressure is in the range of from about 0.4 to about 10.

Claim 21

The process of claim 14 wherein the conditions of temperature and pressure at which the first extraction solvent contacts the slurry are such that the reduced temperature of said first extraction solvent is in the range of from about 1.0 to about 1.25 and the reduced pressure is in the range of from about 0.4 to about 5.

Claim 22

The process of claim 14 wherein the conditions of temperature and pressure at which the second extraction solvent contacts the first heavy phase are such that the reduced temperature of said second extraction solvent is in the range of from about 0.7 to about 1.5 and the reduced pressure is in the range of from about 0.4 to about 10.

Claim 23

The process of claim 14 wherein the conditions of temperature and pressure at which the second extraction solvent contacts the first heavy phase are such that the reduced temperature of said second extraction solvent is in the range of from about 0.8 to about 1.25 and the reduced pressure is in the range of from about 0.4 to about 5.